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Uninsured Idiosyncratic Risk and Aggregate Saving

Author: S. Rao Aiyagari

Quarterly Journal of Economics, 109(3):659–684

https://www.jstor.org/stable/2118417

Notebook by Adam Edwards

Introduction

Aiyigari’s 1994 paper introduces a Bewley model in which heterogenous agents face uninsurable idiosyncratic uncertainty in their income processes. Such uncertainty invokes precautionary saving on the part of the agents. Such models seek to examine the impact of uninsurable idiosyncratic risk on the saving behavior of agents, the aggregate saving rate, and inequality in wealth distributions.

Model

The model is characterized by the following:

max⁡E0(∑t=0∞βtu(ct))s.t.ct+at+1=wℓt+(1+r)atat≥0\begin{split} &\max E_0\left(\sum_{t=0}^\infty \beta^t u(c_t)\right)\\ &\text{s.t.}\\ &c_t+a_{t+1}=w\ell_{t}+(1+r)a_t \\ &a_t\geq 0 \end{split}

where ϕ\phi (if positive) is the limit on borrowing; ℓt\ell_t is assumed to be an i.i.d labor endowment shock with bounded support given by [ℓmin,ℓmax][\ell_{min},\ell_{max}], ℓmin>0\ell_{min}>0; and ww and rr represent the wage and interest rate repectively. The logarithm of the labor endowment shock follows an AR(1) process:

log⁡(ℓt)=ρlog⁡(ℓt−1)+σ(1−ρ2)12ϵt, ϵt∼N(0,1)\begin{split} \log(\ell_t)=\rho\log(\ell_{t-1})+\sigma(1-\rho^2)^{\frac{1}{2}}\epsilon_{t}, \ \epsilon_t \sim N(0,1) \end{split}

The period utility function is assumed to be CRRA, u(c)=c1−μ−11−μu(c) = \frac{c^{1-\mu} - 1}{1 - \mu}.

I wish to find a steady state of this economy; that is, for each combination of parameters, I want to find an interest rate rr such that the saving behavior induced by rr generates capital levels that imply rental rate rr. In other words, I am looking for a fixed point.

To illustrate, I will solve for the fixed point using the parameters of σ=0.2,ρ=0.6,μ=3\sigma = 0.2, \rho = 0.6, \mu = 3. First I import necessary packages.

  1. To begin tackling this problem I need to discretize the income process. Following Aiyagari, I will create a seven-state Markov chain using the Tauchen approximation to the AR1 process.

  1. Next, I will create a MarkovConsumerType with the desired parameters. The T and T_sum parameters define how many periods of the economy to simulate and to average over respectively.

  1. Now, simulate! First, I will input an interest rate of 3% and calculate the resulting capital levels. I display the consumption functions and then the average level of assets during the simulation.

Consumption function by labor endowment level:
<Figure size 640x480 with 1 Axes>
Calculated average normalized aggregate capital between T_sum and T: 1634.0803194370478
<Figure size 640x480 with 1 Axes>

Here I define useful functions for the fixed point problem. As in Aiyagari (1994), I define the capital share to be 0.36 and depreciation rate to be 0.08.

Now I can solve for the equilibrium interest rate. Since consumers cannot borrow, all of the capital stock comes from their saving, and all of the demand for capital comes from firms.

Solving for the equilibrium interest rate:

Input R: 0.99 || Implied R: 1.3684749796221491 || Difference 0.37847497962214915
Input R: 1.05 || Implied R: 0.9345635966454547 || Difference -0.1154364033545453
Input R: 1.035976868644877 || Implied R: 1.0827521670188212 || Difference 0.04677529837394423
Input R: 1.0400205729293608 || Implied R: 1.012215646966888 || Difference -0.02780492596247286
Input R: 1.038513003070935 || Implied R: 1.0406506699575357 || Difference 0.0021376668866006643
Input R: 1.038620631765011 || Implied R: 1.0386517196399538 || Difference 3.10878749427701e-05
Input R: 1.0386222183233766 || Implied R: 1.0386221565430627 || Difference -6.178031397574557e-08
Input R: 1.0386222151766942 || Implied R: 1.0386222151785633 || Difference 1.8691714842589136e-12
Input R: 1.0386222151776947 || Implied R: 1.0386222151599187 || Difference -1.7776002891878306e-11
σ: 0.2 ρ: 0.6 μ: 3 || Interest rate: 3.8622 || Aggregate saving rate: 24.33

This result is very similar to Aiyagari (1994), who calculates the interest rate and saving rate for this combination of parameters as 3.8767 and 24.25 respectively.

The baseline economy

The package aiyagari1994qje, in this repository’s src/, packages the computation above so that other programs can use it: other documents install it from GitHub and compute the same numbers. The cells below use it to describe the baseline economy (σ=0.2\sigma = 0.2, ρ=0.6\rho = 0.6, μ=3\mu = 3) at its equilibrium, after checking that it repeats the computation above exactly: the consumption functions, the distribution of wealth, and the supply of and demand for capital. Each figure is saved as PNG and SVG in baseline/, and every number, with the calibration and a definition of each, in baseline/numbers.json.

Quantities are in levels, for a population of mass one. The labor endowment in state jj is ℓj=exp⁡(xj)\ell_j = \exp(x_j), so aggregate labor supply LL, the population mean of ℓ\ell, is about 1.02 rather than 1. HARK solves the household’s problem with the wage normalized to one; with wage WW, a household with market resources m=(1+r)a+Wℓm = (1+r)a + W\ell consumes Wc(m/W)W c(m/W), and its assets are WW times those of the normalized problem. Every statistic of the distribution comes from the simulation that determines the equilibrium: 1,000 households over the periods that AverageAggregateVar averages, pooled.

Consumption functions. One for each labor endowment state, at the equilibrium interest rate. Below a kink, households consume all their market resources: they would like to borrow and cannot.

The distribution of wealth. The Lorenz curve of end-of-period assets, with the U.S. wealth shares that Krusell and Smith (1998, Table 1) report for the richest 1, 5, 10, 20 and 30 percent of households. Idiosyncratic labor income risk alone produces far less wealth inequality than the data show.

Supply of and demand for capital. Households supply capital by saving: at each interest rate, the supply is their average assets in the simulation. Firms demand capital until its marginal product net of depreciation equals the interest rate. As the interest rate approaches the time-preference rate ϑ=1/β−1\vartheta = 1/\beta - 1, the supply grows without limit; with complete markets the economy would settle at r=ϑr = \vartheta with capital KϑK^\vartheta. Uninsurable risk makes households save more, so the equilibrium has more capital, K∗>KϑK^* > K^\vartheta, at a lower interest rate.

The numbers. Everything above, with the calibration and a definition of each number, goes to baseline/numbers.json. Values are rounded to six significant digits.

Now to solve for equilibrium interest rates for all combinations of parameters:

σ: 0.2 ρ: 0.0 μ: 1
Time to generate shock history: 3.828915000000002
Input R: 0.99 || Implied R: 1.9837698242432893 || Difference 0.9937698242432893
Input R: 1.05 || Implied R: 0.920854202334329 || Difference -0.12914579766567102
Input R: 1.043099438899276 || Implied R: 0.9499624293592571 || Difference -0.09313700954001891
Input R: 1.0267805090471234 || Implied R: 1.572528047169771 || Difference 0.5457475381226475
Input R: 1.0407204545727913 || Implied R: 1.1484947639834655 || Difference 0.10777430941067423
Input R: 1.041996606629454 || Implied R: 0.9928439186718966 || Difference -0.04915268795755734
Input R: 1.041150205130333 || Implied R: 1.0971319278524572 || Difference 0.055981722722124205
Input R: 1.0416008950017943 || Implied R: 1.0338878682939183 || Difference -0.007713026707875992
Input R: 1.041536161354706 || Implied R: 1.0424728621394181 || Difference 0.0009367007847120856
Input R: 1.0415431715244572 || Implied R: 1.0415240851724894 || Difference -1.908635196778974e-05
Input R: 1.0415430315366272 || Implied R: 1.041542991047995 || Difference -4.048863222472221e-08
Input R: 1.041543031239047 || Implied R: 1.041543031239347 || Difference 2.999822612537173e-13
Input R: 1.0415430312400475 || Implied R: 1.0415430311042244 || Difference -1.3582313052040718e-10
σ: 0.2 ρ: 0.0 μ: 1 || Interest rate: 4.1543 || Aggregate saving rate: 23.85

σ: 0.2 ρ: 0.0 μ: 3
Time to generate shock history: 3.7599969999999985
Input R: 0.99 || Implied R: 1.4829122892954594 || Difference 0.4929122892954594
Input R: 1.05 || Implied R: 0.9352027032606937 || Difference -0.11479729673930639
Input R: 1.0386659056189969 || Implied R: 1.141033995452829 || Difference 0.10236808983383217
Input R: 1.0440086059916869 || Implied R: 0.9672320318095836 || Difference -0.07677657418210326
Input R: 1.041718868623567 || Implied R: 1.01693000762891 || Difference -0.024788860994656936
Input R: 1.0408399148722671 || Implied R: 1.0531005644803497 || Difference 0.012260649608082597
Input R: 1.0411307835987653 || Implied R: 1.0402633220999546 || Difference -0.0008674614988106732
Input R: 1.041111563970032 || Implied R: 1.0410911130248919 || Difference -2.0450945140026988e-05
Input R: 1.041111100687687 || Implied R: 1.0411111084230933 || Difference 7.735406315489968e-09
Input R: 1.0411111008628535 || Implied R: 1.0411111008624847 || Difference -3.68816088780477e-13
Input R: 1.041111100861853 || Implied R: 1.0411111009056717 || Difference 4.381872642511553e-11
σ: 0.2 ρ: 0.0 μ: 3 || Interest rate: 4.1111 || Aggregate saving rate: 23.92

σ: 0.2 ρ: 0.0 μ: 5
Time to generate shock history: 3.768706999999992
Input R: 0.99 || Implied R: 1.3539661658773678 || Difference 0.36396616587736785
Input R: 1.05 || Implied R: 0.9475976272851615 || Difference -0.10240237271483854
Input R: 1.0368255642170092 || Implied R: 1.1265278686265883 || Difference 0.08970230440957905
Input R: 1.042977300170137 || Implied R: 0.9910909750958089 || Difference -0.05188632507432811
Input R: 1.0407229456178055 || Implied R: 1.0336091737037483 || Difference -0.007113771914057265
Input R: 1.040391076822961 || Implied R: 1.0417909932547527 || Difference 0.0013999164317917145
Input R: 1.0404456464243168 || Implied R: 1.0404224204381334 || Difference -2.3225986183428304e-05
Input R: 1.0404447558368457 || Implied R: 1.0404446898375124 || Difference -6.599933333184538e-08
Input R: 1.040444753299046 || Implied R: 1.040444753298943 || Difference -1.0302869668521453e-13
Input R: 1.0404447532980454 || Implied R: 1.0404447533239647 || Difference 2.5919266732898905e-11
σ: 0.2 ρ: 0.0 μ: 5 || Interest rate: 4.0445 || Aggregate saving rate: 24.04

σ: 0.2 ρ: 0.3 μ: 1
Time to generate shock history: 3.8032089999999954
Input R: 0.99 || Implied R: 2.018727393794474 || Difference 1.028727393794474
Input R: 1.05 || Implied R: 0.9208573070498646 || Difference -0.12914269295013547
Input R: 1.0433079179903564 || Implied R: 0.9459233057713744 || Difference -0.09738461221898198
Input R: 1.0245615964704229 || Implied R: 1.5382913648119914 || Difference 0.5137297683415685
Input R: 1.0403205831970292 || Implied R: 1.12705054789323 || Difference 0.08672996469620076
Input R: 1.0417278125728997 || Implied R: 1.0045390415697142 || Difference -0.03718877100318552
Input R: 1.0413054944245355 || Implied R: 1.0425525466942387 || Difference 0.0012470522697032305
Input R: 1.0413191965586543 || Implied R: 1.041216302970888 || Difference -0.00010289358776627289
Input R: 1.0413181521747394 || Implied R: 1.0413180597447953 || Difference -9.242994414293548e-08
Input R: 1.041318151235789 || Implied R: 1.0413181512362122 || Difference 4.2321701698710967e-13
Input R: 1.0413181512367895 || Implied R: 1.0413181511387142 || Difference -9.807532563854693e-11
σ: 0.2 ρ: 0.3 μ: 1 || Interest rate: 4.1318 || Aggregate saving rate: 23.85

σ: 0.2 ρ: 0.3 μ: 3
Time to generate shock history: 3.7839560000000034
Input R: 0.99 || Implied R: 1.4166035804138741 || Difference 0.42660358041387414
Input R: 1.05 || Implied R: 0.9350020624840051 || Difference -0.11499793751599496
Input R: 1.0372602346512383 || Implied R: 1.12023022176166 || Difference 0.0829699871104217
Input R: 1.0425995751972952 || Implied R: 0.9829694606330489 || Difference -0.05963011456424627
Input R: 1.0403668594788642 || Implied R: 1.038403275276933 || Difference -0.001963584201931212
Input R: 1.0402925916421184 || Implied R: 1.0406639781472011 || Difference 0.00037138650508272697
Input R: 1.0403044042409857 || Implied R: 1.0403039933809286 || Difference -4.1086005708734774e-07
Input R: 1.0403043911873024 || Implied R: 1.0403043911079006 || Difference -7.940181845356165e-11
Input R: 1.0403043911847791 || Implied R: 1.0403043911847825 || Difference 3.3306690738754696e-15
Input R: 1.0403043911857797 || Implied R: 1.0403043911542988 || Difference -3.1480817952456164e-11
σ: 0.2 ρ: 0.3 μ: 3 || Interest rate: 4.0304 || Aggregate saving rate: 24.04

σ: 0.2 ρ: 0.3 μ: 5
Time to generate shock history: 3.7417290000000065
Input R: 0.99 || Implied R: 1.2879144564687075 || Difference 0.2979144564687075
Input R: 1.05 || Implied R: 0.9464950414684935 || Difference -0.10350495853150654
Input R: 1.0345291550935893 || Implied R: 1.10510328311729 || Difference 0.07057412802370067
Input R: 1.0408012548079544 || Implied R: 1.0078862884129987 || Difference -0.032914966394955725
Input R: 1.0388063977412862 || Implied R: 1.0407504675054715 || Difference 0.0019440697641852633
Input R: 1.0389176498507673 || Implied R: 1.0388199202842106 || Difference -9.772956655673681e-05
Input R: 1.0389123248316656 || Implied R: 1.038912298697576 || Difference -2.6134089559093354e-08
Input R: 1.0389123234073283 || Implied R: 1.038912323407809 || Difference 4.807265696626928e-13
Input R: 1.0389123234083288 || Implied R: 1.0389123233904523 || Difference -1.7876589097909346e-11
σ: 0.2 ρ: 0.3 μ: 5 || Interest rate: 3.8912 || Aggregate saving rate: 24.31

σ: 0.2 ρ: 0.6 μ: 1
Time to generate shock history: 3.829779000000002
Input R: 0.99 || Implied R: 2.2628775714617992 || Difference 1.2728775714617993
Input R: 1.05 || Implied R: 0.9208638096630398 || Difference -0.12913619033696022
Input R: 1.0444735411082722 || Implied R: 0.9336346244886672 || Difference -0.11083891661960499
Input R: 1.017236770554136 || Implied R: 1.6448528463595131 || Difference 0.627616075805377
Input R: 1.0403854190542474 || Implied R: 1.0682716163282484 || Difference 0.02788619727400099
Input R: 1.0412072037684856 || Implied R: 1.0185363672072287 || Difference -0.022670836561256902
Input R: 1.0408386982306461 || Implied R: 1.0415012011764366 || Difference 0.0006625029457905107
Input R: 1.0408491611994932 || Implied R: 1.0408543717683414 || Difference 5.210568848168506e-06
Input R: 1.0408492441237658 || Implied R: 1.040849242029509 || Difference -2.0942567680037882e-09
Input R: 1.0408492440904498 || Implied R: 1.0408492440904769 || Difference 2.708944180085382e-14
Input R: 1.0408492440914503 || Implied R: 1.0408492440285853 || Difference -6.286504650176994e-11
σ: 0.2 ρ: 0.6 μ: 1 || Interest rate: 4.0849 || Aggregate saving rate: 23.89

σ: 0.2 ρ: 0.6 μ: 3
Time to generate shock history: 3.771885999999995
Input R: 0.99 || Implied R: 1.3684749796221491 || Difference 0.37847497962214915
Input R: 1.05 || Implied R: 0.9345635966454547 || Difference -0.1154364033545453
Input R: 1.035976868644877 || Implied R: 1.0827521670188212 || Difference 0.04677529837394423
Input R: 1.0400205729293608 || Implied R: 1.012215646966888 || Difference -0.02780492596247286
Input R: 1.038513003070935 || Implied R: 1.0406506699575357 || Difference 0.0021376668866006643
Input R: 1.038620631765011 || Implied R: 1.0386517196399538 || Difference 3.10878749427701e-05
Input R: 1.0386222183233766 || Implied R: 1.0386221565430627 || Difference -6.178031397574557e-08
Input R: 1.0386222151766942 || Implied R: 1.0386222151785633 || Difference 1.8691714842589136e-12
Input R: 1.0386222151776947 || Implied R: 1.0386222151599187 || Difference -1.7776002891878306e-11
σ: 0.2 ρ: 0.6 μ: 3 || Interest rate: 3.8622 || Aggregate saving rate: 24.33

σ: 0.2 ρ: 0.6 μ: 5
Time to generate shock history: 3.815433000000013
Input R: 0.99 || Implied R: 1.2264940454316713 || Difference 0.2364940454316713
Input R: 1.05 || Implied R: 0.9445652454686938 || Difference -0.10543475453130624
Input R: 1.0314988229345896 || Implied R: 1.0748918021762413 || Difference 0.04339297924165164
Input R: 1.0368931212417196 || Implied R: 1.0240202195684134 || Difference -0.012872901673306236
Input R: 1.035658975955536 || Implied R: 1.0369667349237233 || Difference 0.0013077589681873558
Input R: 1.0357727904389973 || Implied R: 1.0357945787187934 || Difference 2.1788279796153276e-05
Input R: 1.0357747155463535 || Implied R: 1.0357747041213183 || Difference -1.1425035140177897e-08
Input R: 1.0357747145374214 || Implied R: 1.0357747145377971 || Difference 3.7569947153315297e-13
Input R: 1.035774714538422 || Implied R: 1.035774714527468 || Difference -1.0953904450161644e-11
σ: 0.2 ρ: 0.6 μ: 5 || Interest rate: 3.5775 || Aggregate saving rate: 24.92

σ: 0.2 ρ: 0.9 μ: 1
Time to generate shock history: 3.7833669999999984
Input R: 0.99 || Implied R: 14.951106335333938 || Difference 13.961106335333938
Input R: 1.05 || Implied R: 0.9209013384282211 || Difference -0.12909866157177896
Input R: 1.0494502621007993 || Implied R: 0.9211932166683504 || Difference -0.12825704543244887
Input R: 1.0197251310503996 || Implied R: 2.118433499651733 || Difference 1.0987083686013333
Input R: 1.0463430372026803 || Implied R: 0.9254900850860207 || Difference -0.12085295211665958
Input R: 1.03303408412654 || Implied R: 1.2744665501006116 || Difference 0.24143246597407164
Input R: 1.0419033711589567 || Implied R: 0.9648249090964772 || Difference -0.07707846206247948
Input R: 1.035977754110141 || Implied R: 1.1618734673300672 || Difference 0.12589571321992632
Input R: 1.0396531467239591 || Implied R: 1.0331248546523102 || Difference -0.006528292071648956
Input R: 1.0394551894014057 || Implied R: 1.0399644901568852 || Difference 0.0005093007554795026
Input R: 1.0394695152961264 || Implied R: 1.0394689235943935 || Difference -5.917017329437613e-07
Input R: 1.0394694986717252 || Implied R: 1.0394694983365718 || Difference -3.351534605400275e-10
Input R: 1.0394694986623034 || Implied R: 1.039469498662302 || Difference -1.3322676295501878e-15
Input R: 1.039469498661303 || Implied R: 1.0394694986968949 || Difference 3.559197381264312e-11
σ: 0.2 ρ: 0.9 μ: 1 || Interest rate: 3.9469 || Aggregate saving rate: 24.15

σ: 0.2 ρ: 0.9 μ: 3
Time to generate shock history: 3.7742470000000026
Input R: 0.99 || Implied R: 1.4767080084748145 || Difference 0.48670800847481455
Input R: 1.05 || Implied R: 0.9334544598667381 || Difference -0.1165455401332619
Input R: 1.0384083029032645 || Implied R: 0.9869477353125718 || Difference -0.05146056759069262
Input R: 1.0301195149991496 || Implied R: 1.0642570149010335 || Difference 0.03413749990188397
Input R: 1.0334251795375224 || Implied R: 1.0332133504080525 || Difference -0.0002118291294699315
Input R: 1.0334047938106035 || Implied R: 1.0334066534679092 || Difference 1.859657305702811e-06
Input R: 1.0334049712203148 || Implied R: 1.0334049713029065 || Difference 8.259171124791465e-11
Input R: 1.0334049712281943 || Implied R: 1.0334049712281936 || Difference -6.661338147750939e-16
Input R: 1.0334049712271938 || Implied R: 1.0334049712376807 || Difference 1.0486944646004304e-11
σ: 0.2 ρ: 0.9 μ: 3 || Interest rate: 3.3405 || Aggregate saving rate: 25.43

σ: 0.2 ρ: 0.9 μ: 5
Time to generate shock history: 3.769485000000003
Input R: 0.99 || Implied R: 1.1767517564255607 || Difference 0.18675175642556074
Input R: 1.05 || Implied R: 0.9406091599167042 || Difference -0.1093908400832958
Input R: 1.027836858046183 || Implied R: 1.0174850877454755 || Difference -0.010351770300707441
Input R: 1.0256419834991088 || Implied R: 1.0283674384784427 || Difference 0.0027254549793338523
Input R: 1.0260994224156401 || Implied R: 1.026113179252782 || Difference 1.3756837141887246e-05
Input R: 1.0261017399895624 || Implied R: 1.0261017375732269 || Difference -2.416335576072015e-09
Input R: 1.026101739582561 || Implied R: 1.0261017395825796 || Difference 1.865174681370263e-14
Input R: 1.0261017395835614 || Implied R: 1.0261017395776404 || Difference -5.921041434930885e-12
σ: 0.2 ρ: 0.9 μ: 5 || Interest rate: 2.6102 || Aggregate saving rate: 27.17

σ: 0.4 ρ: 0.0 μ: 1
Time to generate shock history: 3.7715670000000046
Input R: 0.99 || Implied R: 1.3826553740730105 || Difference 0.39265537407301054
Input R: 1.05 || Implied R: 0.9208507342345064 || Difference -0.12914926576549368
Input R: 1.0351496990361606 || Implied R: 1.1598355236255207 || Difference 0.12468582458936006
Input R: 1.0424442855272875 || Implied R: 0.9601239021608644 || Difference -0.08232038336642311
Input R: 1.0395434394010816 || Implied R: 1.0755114757677449 || Difference 0.035968036366663236
Input R: 1.040425501560648 || Implied R: 1.044011943519654 || Difference 0.003586441959005926
Input R: 1.0405191163541296 || Implied R: 1.040046812020911 || Difference -0.00047230433321865384
Input R: 1.0405082226767643 || Implied R: 1.0405146934497598 || Difference 6.470772995426088e-06
Input R: 1.0405083699077136 || Implied R: 1.0405083810202802 || Difference 1.111256664465543e-08
Input R: 1.0405083701609894 || Implied R: 1.0405083701610243 || Difference 3.4861002973229915e-14
Input R: 1.04050837016199 || Implied R: 1.0405083701181281 || Difference -4.3861803078470984e-11
σ: 0.4 ρ: 0.0 μ: 1 || Interest rate: 4.0508 || Aggregate saving rate: 23.92

σ: 0.4 ρ: 0.0 μ: 3
Time to generate shock history: 3.8172270000000026
Input R: 0.99 || Implied R: 1.1885728910231683 || Difference 0.19857289102316833
Input R: 1.05 || Implied R: 0.9341781379814148 || Difference -0.11582186201858524
Input R: 1.0278962223323358 || Implied R: 1.11052986567286 || Difference 0.08263364334052414
Input R: 1.0370998757001921 || Implied R: 1.0421068594078013 || Difference 0.005006983707609214
Input R: 1.0376689191773951 || Implied R: 1.0350746505437178 || Difference -0.002594268633677288
Input R: 1.0374747075425454 || Implied R: 1.0375302555453059 || Difference 5.554800276041938e-05
Input R: 1.0374787787934692 || Implied R: 1.0374793687903925 || Difference 5.8999692331696e-07
Input R: 1.0374788224900942 || Implied R: 1.0374788224916827 || Difference 1.588507103633674e-12
Input R: 1.0374788224910947 || Implied R: 1.0374788224791738 || Difference -1.1920908704610156e-11
σ: 0.4 ρ: 0.0 μ: 3 || Interest rate: 3.7479 || Aggregate saving rate: 24.53

σ: 0.4 ρ: 0.0 μ: 5
Time to generate shock history: 3.808525000000003
Input R: 0.99 || Implied R: 1.1293618190950938 || Difference 0.13936181909509382
Input R: 1.05 || Implied R: 0.943643600378219 || Difference -0.106356399621781
Input R: 1.0240296669468383 || Implied R: 1.0794177744327411 || Difference 0.05538810748590284
Input R: 1.0329229989326691 || Implied R: 1.0392019558402246 || Difference 0.006278956907555422
Input R: 1.0339966878589482 || Implied R: 1.032123972975053 || Difference -0.0018727148838950658
Input R: 1.0337500251762055 || Implied R: 1.033804566238595 || Difference 5.454106238955703e-05
Input R: 1.033757005694177 || Implied R: 1.033757455897782 || Difference 4.5020360506242696e-07
Input R: 1.0337570637797595 || Implied R: 1.0337570637767426 || Difference -3.0169200471164004e-12
Input R: 1.033757063778759 || Implied R: 1.0337570637834967 || Difference 4.737765735285393e-12
σ: 0.4 ρ: 0.0 μ: 5 || Interest rate: 3.3757 || Aggregate saving rate: 25.33

σ: 0.4 ρ: 0.3 μ: 1
Time to generate shock history: 3.857618000000002
Input R: 0.99 || Implied R: 1.3473876236636784 || Difference 0.3573876236636784
Input R: 1.05 || Implied R: 0.9208495930658519 || Difference -0.12915040693414814
Input R: 1.0340731372909793 || Implied R: 1.1278716730932752 || Difference 0.09379853580229591
Input R: 1.0407738481519244 || Implied R: 1.0048512327021355 || Difference -0.03592261544978892
Input R: 1.0389182752004464 || Implied R: 1.0557309662317274 || Difference 0.016812691031280913
Input R: 1.0395098556197315 || Implied R: 1.041930153809039 || Difference 0.002420298189307557
Input R: 1.0396030591795131 || Implied R: 1.0395657809156216 || Difference -3.72782638915492e-05
Input R: 1.0396016454017678 || Implied R: 1.039602066124806 || Difference 4.207230381858551e-07
Input R: 1.0396016611796153 || Implied R: 1.039601661261414 || Difference 8.179878996372736e-11
Input R: 1.0396016611826835 || Implied R: 1.0396016611826844 || Difference 8.881784197001252e-16
Input R: 1.039601661183684 || Implied R: 1.039601661157009 || Difference -2.667510656806371e-11
σ: 0.4 ρ: 0.3 μ: 1 || Interest rate: 3.9602 || Aggregate saving rate: 24.09

σ: 0.4 ρ: 0.3 μ: 3
Time to generate shock history: 3.886445000000009
Input R: 0.99 || Implied R: 1.145759956340119 || Difference 0.15575995634011908
Input R: 1.05 || Implied R: 0.9335156821260359 || Difference -0.11648431787396418
Input R: 1.0243279850692402 || Implied R: 1.084136113239646 || Difference 0.05980812817040593
Input R: 1.033037349502161 || Implied R: 1.0431740639393823 || Difference 0.010136714437221306
Input R: 1.0346724285955267 || Implied R: 1.0319353689117732 || Difference -0.0027370596837534844
Input R: 1.0343247986756487 || Implied R: 1.0344630862451303 || Difference 0.0001382875694815322
Input R: 1.0343415176638144 || Implied R: 1.0343433112841143 || Difference 1.7936202998392048e-06
Input R: 1.0343417372184431 || Implied R: 1.03434173720158 || Difference -1.6863177521031503e-11
Input R: 1.034341737216379 || Implied R: 1.0343417372163783 || Difference -6.661338147750939e-16
Input R: 1.0343417372153785 || Implied R: 1.034341737223552 || Difference 8.173461907290402e-12
σ: 0.4 ρ: 0.3 μ: 3 || Interest rate: 3.4342 || Aggregate saving rate: 25.2

σ: 0.4 ρ: 0.3 μ: 5
Time to generate shock history: 3.839375000000018
Input R: 0.99 || Implied R: 1.0908741517999845 || Difference 0.10087415179998449
Input R: 1.05 || Implied R: 0.9416761713002942 || Difference -0.1083238286997058
Input R: 1.018931680380194 || Implied R: 1.0557141812662625 || Difference 0.03678250088606849
Input R: 1.0313268107504272 || Implied R: 1.0157243754450687 || Difference -0.015602435305358542
Input R: 1.0276350200608988 || Implied R: 1.0307789492758714 || Difference 0.0031439292149726406
Input R: 1.028254165633993 || Implied R: 1.0284793072828555 || Difference 0.00022514164886255905
Input R: 1.0283012442929782 || Implied R: 1.0283009391701041 || Difference -3.051228740780232e-07
Input R: 1.0283011805760502 || Implied R: 1.028301180914851 || Difference 3.3880076522052605e-10
Input R: 1.0283011806467215 || Implied R: 1.028301180646722 || Difference 4.440892098500626e-16
Input R: 1.028301180647722 || Implied R: 1.0283011806429256 || Difference -4.796385510985601e-12
σ: 0.4 ρ: 0.3 μ: 5 || Interest rate: 2.8301 || Aggregate saving rate: 26.6

σ: 0.4 ρ: 0.6 μ: 1
Time to generate shock history: 3.8022040000000175
Input R: 0.99 || Implied R: 1.336359257603068 || Difference 0.34635925760306807
Input R: 1.05 || Implied R: 0.9208443180627103 || Difference -0.12915568193728977
Input R: 1.0337032650883102 || Implied R: 1.0867230822481866 || Difference 0.05301981715987636
Input R: 1.0384462185019299 || Implied R: 1.0281168664474627 || Difference -0.010329352054467167
Input R: 1.0376728597318812 || Implied R: 1.039878820609141 || Difference 0.0022059608772597716
Input R: 1.0378089551927687 || Implied R: 1.0378968516158293 || Difference 8.789642306061829e-05
Input R: 1.0378145552920577 || Implied R: 1.0378145449570717 || Difference -1.0334985978133204e-08
Input R: 1.0378145546336675 || Implied R: 1.037814554636892 || Difference 3.2245317527213047e-12
Input R: 1.037814554634668 || Implied R: 1.0378145546221829 || Difference -1.248512404572466e-11
σ: 0.4 ρ: 0.6 μ: 1 || Interest rate: 3.7815 || Aggregate saving rate: 24.44

σ: 0.4 ρ: 0.6 μ: 3
Time to generate shock history: 3.7896399999999915
Input R: 0.99 || Implied R: 1.1047171314292412 || Difference 0.11471713142924123
Input R: 1.05 || Implied R: 0.9324774307840086 || Difference -0.11752256921599147
Input R: 1.0196376022989666 || Implied R: 1.0564728008272641 || Difference 0.03683519852829753
Input R: 1.0303100036044461 || Implied R: 1.0206237549245767 || Difference -0.009686248679869447
Input R: 1.0280878987633464 || Implied R: 1.0296616654572335 || Difference 0.001573766693887091
Input R: 1.0283984733472318 || Implied R: 1.0284596959069454 || Difference 6.122255971363622e-05
Input R: 1.0284109653764706 || Implied R: 1.028410884195227 || Difference -8.118124350531275e-08
Input R: 1.0284109488339488 || Implied R: 1.0284109487568873 || Difference -7.706146831765182e-11
Input R: 1.028410948818231 || Implied R: 1.0284109488182305 || Difference -4.440892098500626e-16
Input R: 1.0284109488172304 || Implied R: 1.0284109488221354 || Difference 4.9049653227939416e-12
σ: 0.4 ρ: 0.6 μ: 3 || Interest rate: 2.8411 || Aggregate saving rate: 26.56

σ: 0.4 ρ: 0.6 μ: 5
Time to generate shock history: 3.7792180000000144
Input R: 0.99 || Implied R: 1.0535064074377145 || Difference 0.06350640743771452
Input R: 1.05 || Implied R: 0.9391432337057125 || Difference -0.11085676629428753
Input R: 1.011853149175407 || Implied R: 1.0310053489805848 || Difference 0.019152199805177794
Input R: 1.0198992740876123 || Implied R: 1.0164220650256717 || Difference -0.0034772090619406004
Input R: 1.0186629157442497 || Implied R: 1.0189703047677816 || Difference 0.0003073890235318899
Input R: 1.018763334064853 || Implied R: 1.0187678059596208 || Difference 4.471894767821283e-06
Input R: 1.0187648146129764 || Implied R: 1.0187648151537816 || Difference 5.408051784172585e-10
Input R: 1.0187648147920436 || Implied R: 1.0187648147920434 || Difference -2.220446049250313e-16
Input R: 1.018764814791043 || Implied R: 1.0187648147940647 || Difference 3.021582983819826e-12
σ: 0.4 ρ: 0.6 μ: 5 || Interest rate: 1.8765 || Aggregate saving rate: 29.16

σ: 0.4 ρ: 0.9 μ: 1
Time to generate shock history: 3.799363999999997
Input R: 0.99 || Implied R: 1.7105557932471975 || Difference 0.7205557932471975
Input R: 1.05 || Implied R: 0.9208534148679469 || Difference -0.12914658513205313
Input R: 1.040880577358506 || Implied R: 0.9601854201080408 || Difference -0.08069515725046517
Input R: 1.0272219425947806 || Implied R: 1.1002497544992165 || Difference 0.07302781190443586
Input R: 1.0337106294571299 || Implied R: 1.0352954015257598 || Difference 0.0015847720686299471
Input R: 1.033851791281147 || Implied R: 1.0338970083848351 || Difference 4.521710368821097e-05
Input R: 1.0338559332008128 || Implied R: 1.0338559664858111 || Difference 3.328499831312115e-08
Input R: 1.0338559362519029 || Implied R: 1.0338559362527984 || Difference 8.955058916626513e-13
Input R: 1.0338559362529034 || Implied R: 1.0338559362428836 || Difference -1.0019762797242038e-11
σ: 0.4 ρ: 0.9 μ: 1 || Interest rate: 3.3856 || Aggregate saving rate: 25.32

σ: 0.4 ρ: 0.9 μ: 3
Time to generate shock history: 3.813907000000029
Input R: 0.99 || Implied R: 1.0612353173305715 || Difference 0.07123531733057153
Input R: 1.05 || Implied R: 0.9306769481602285 || Difference -0.11932305183977154
Input R: 1.01242944803969 || Implied R: 1.0196197535925042 || Difference 0.007190305552814191
Input R: 1.014804475273501 || Implied R: 1.0145076919613654 || Difference -0.00029678331213567333
Input R: 1.0147103307452903 || Implied R: 1.0147132823965397 || Difference 2.9516512494165426e-06
Input R: 1.014711257837049 || Implied R: 1.0147112589121374 || Difference 1.075088462698659e-09
Input R: 1.014711258174848 || Implied R: 1.0147112581748474 || Difference -6.661338147750939e-16
Input R: 1.0147112581738476 || Implied R: 1.0147112581770312 || Difference 3.183675545415099e-12
σ: 0.4 ρ: 0.9 μ: 3 || Interest rate: 1.4711 || Aggregate saving rate: 30.43

σ: 0.4 ρ: 0.9 μ: 5
Time to generate shock history: 3.7791540000000055
Input R: 0.99 || Implied R: 1.0063061205248935 || Difference 0.016306120524893553
Input R: 1.05 || Implied R: 0.9352770224031702 || Difference -0.11472297759682981
Input R: 0.9974667936017138 || Implied R: 0.9995483843887504 || Difference 0.0020815907870366246
Input R: 0.9985399973174669 || Implied R: 0.9984846848917922 || Difference -5.5312425674691745e-05
Input R: 0.9985122180991999 || Implied R: 0.9985125166900756 || Difference 2.9859087569139575e-07
Input R: 0.9985123672534795 || Implied R: 0.998512367294376 || Difference 4.0896508401999654e-11
Input R: 0.9985123672739111 || Implied R: 0.9985123672739112 || Difference 1.1102230246251565e-16
Input R: 0.9985123672749115 || Implied R: 0.9985123672729092 || Difference -2.0023982472139323e-12
σ: 0.4 ρ: 0.9 μ: 5 || Interest rate: -0.1488 || Aggregate saving rate: 36.7

Table II, Aiyagari (1994)
Net return to capital in % / aggregate saving rate in % (σ = 0.2)
                µ = 1         µ = 3         µ = 5
ρ = 0    4.1666/23.67  4.1456/23.71  4.0858/23.83
ρ = 0.3  4.1365/23.73  4.0432/23.91  3.9054/24.19
ρ = 0.6  4.0912/23.82  3.8767/24.25  3.5857/24.86
ρ = 0.9  3.9305/24.14  3.2903/25.51  2.5260/27.36
Net return to capital in % / aggregate saving rate in % (σ = 0.4)
                µ = 1         µ = 3          µ = 5
ρ = 0    4.0649/23.87  3.7816/24.44   3.4177/25.22
ρ = 0.3  3.9554/24.09  3.4188/25.22   2.8032/26.66
ρ = 0.6  3.7567/24.50  2.7835/26.71   1.8070/29.37
ρ = 0.9  3.3054/25.47  1.2894/31.00  -0.3456/37.63


Table II, Replication (HARK)
Net return to capital in % / aggregate saving rate in % (σ = 0.2)
                µ = 1         µ = 3         µ = 5
ρ = 0    4.1543/23.85  4.1111/23.92  4.0445/24.04
ρ = 0.3  4.1318/23.85  4.0304/24.04  3.8912/24.31
ρ = 0.6  4.0849/23.89  3.8622/24.33  3.5775/24.92
ρ = 0.9  3.9469/24.15  3.3405/25.43  2.6102/27.17
Net return to capital in % / aggregate saving rate in % (σ = 0.4)
                µ = 1         µ = 3          µ = 5
ρ = 0    4.0508/23.92  3.7479/24.53   3.3757/25.33
ρ = 0.3  3.9602/24.09  3.4342/25.20   2.8301/26.60
ρ = 0.6  3.7815/24.44  2.8411/26.56   1.8765/29.16
ρ = 0.9  3.3856/25.32  1.4711/30.43  -0.1488/36.70


HARK minus Aiyagari (1994)
Net return to capital in % / aggregate saving rate in % (σ = 0.2)
                µ = 1         µ = 3         µ = 5
ρ = 0    -0.0123/0.18  -0.0345/0.21  -0.0413/0.21
ρ = 0.3  -0.0047/0.12  -0.0128/0.13  -0.0142/0.12
ρ = 0.6  -0.0063/0.07  -0.0145/0.08  -0.0082/0.06
ρ = 0.9   0.0164/0.01  0.0502/-0.08  0.0842/-0.19
Net return to capital in % / aggregate saving rate in % (σ = 0.4)
                µ = 1         µ = 3         µ = 5
ρ = 0    -0.0141/0.05  -0.0337/0.09  -0.0420/0.11
ρ = 0.3   0.0048/0.00  0.0154/-0.02  0.0269/-0.06
ρ = 0.6  0.0248/-0.06  0.0576/-0.15  0.0695/-0.21
ρ = 0.9  0.0802/-0.15  0.1817/-0.57  0.1968/-0.93