第11章のRコード

第11章 操作変数法

サンプルデータ

cigarette.csv：母親の喫煙と新生児の出生体重に関する架空データ．

proximity.csv：Card (1995)のデータ．

パッケージの読み込み

library(dplyr)
library(broom)
library(fixest)

11.2 操作変数法の実施：2段階最小二乗法

11.2.1 2段階最小二乗法

cigdata <- readr::read_csv("cigarette.csv")

cigdata %>% # 通常の最小二乗法
  lm(bw ~ cigpacks,
     data = .) %>% 
  tidy()
# A tibble: 2 × 5
  term        estimate std.error statistic   p.value
  <chr>          <dbl>     <dbl>     <dbl>     <dbl>
1 (Intercept)   3423.      17.0      201.  0        
2 cigpacks       -62.4      1.54     -40.4 2.94e-212
cigdata %>% 
  lm(cigpacks ~ price,
     data = .) %>% 
  augment(newdata = cigdata) %>% 
  lm(bw ~ .fitted,
     data = .) %>% 
  tidy()
# A tibble: 2 × 5
  term        estimate std.error statistic   p.value
  <chr>          <dbl>     <dbl>     <dbl>     <dbl>
1 (Intercept)   3332.      22.2      150.  0        
2 .fitted        -53.3      2.03     -26.2 1.63e-115
cigdata %>% 
  lm(cigpacks ~ price,
     data = .) %>% 
  tidy()
# A tibble: 2 × 5
  term        estimate std.error statistic p.value
  <chr>          <dbl>     <dbl>     <dbl>   <dbl>
1 (Intercept)    42.1     0.340      124.        0
2 price          -5.01    0.0526     -95.2       0

Rによるデータ演習

proxdata <- readr::read_csv("proximity.csv")

proxdata %>% 
  print(n = 4)
# A tibble: 3,010 × 7
  lwage  educ exper black south  smsa nearc4
  <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>  <dbl>
1  6.31     7    16     1     0     1      0
2  6.18    12     9     0     0     1      0
3  6.58    12    16     0     0     1      0
4  5.52    11    10     0     0     1      1
# ℹ 3,006 more rows
OLS <- proxdata %>% # 最小二乗法 
  feols(lwage ~ educ + exper + black + south + smsa)

OLS
OLS estimation, Dep. Var.: lwage
Observations: 3,010 
Standard-errors: IID 
             Estimate Std. Error   t value  Pr(>|t|)    
(Intercept)  4.913331   0.063121  77.83968 < 2.2e-16 ***
educ         0.073807   0.003534  20.88707 < 2.2e-16 ***
exper        0.039313   0.002196  17.90611 < 2.2e-16 ***
black       -0.188223   0.017768 -10.59349 < 2.2e-16 ***
south       -0.129053   0.015229  -8.47442 < 2.2e-16 ***
smsa         0.164741   0.015692  10.49851 < 2.2e-16 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
RMSE: 0.376836   Adj. R2: 0.277561
TSLS <- proxdata %>% # 2段階最小二乗法 
  feols(lwage ~ exper + black + south + smsa | educ ~ nearc4)

TSLS
TSLS estimation, Dep. Var.: lwage, Endo.: educ, Instr.: nearc4
Second stage: Dep. Var.: lwage
Observations: 3,010 
Standard-errors: IID 
             Estimate Std. Error  t value   Pr(>|t|)    
(Intercept)  3.939822   0.831763  4.73671 2.2729e-06 ***
fit_educ     0.131850   0.049573  2.65970 7.8625e-03 ** 
exper        0.062270   0.019686  3.16313 1.5764e-03 ** 
black       -0.129601   0.053262 -2.43326 1.5022e-02 *  
south       -0.109252   0.023176 -4.71394 2.5403e-06 ***
smsa         0.134826   0.030291  4.45105 8.8561e-06 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
RMSE: 0.393395   Adj. R2: 0.212674
F-test (1st stage), educ: stat = 16.7    , p = 4.43e-5 , on 1 and 3,004 DoF.
              Wu-Hausman: stat =  1.50259, p = 0.220369, on 1 and 3,003 DoF.
etable(OLS, TSLS)
                                OLS                TSLS
Dependent Var.:               lwage               lwage
                                                       
Constant          4.913*** (0.0631)   3.940*** (0.8318)
educ             0.0738*** (0.0035)   0.1318** (0.0496)
exper            0.0393*** (0.0022)   0.0623** (0.0197)
black           -0.1882*** (0.0178)   -0.1296* (0.0533)
south           -0.1291*** (0.0152) -0.1093*** (0.0232)
smsa             0.1647*** (0.0157)  0.1348*** (0.0303)
_______________ ___________________ ___________________
S.E. type                       IID                 IID
Observations                  3,010               3,010
R2                          0.27876             0.21398
Adj. R2                     0.27756             0.21267
---
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1