关键词 > ECMT6002/6702
ECMT 6002/6702: Econometric Applications
发布时间:2023-06-03
Hello, dear friend, you can consult us at any time if you have any questions, add WeChat: daixieit
ECMT 6002/6702: Econometric Applications
yt = β 1 + β2 x2t + β3x3t + ut, Cov(xjt, ut) = 0,
wage education (1.1)
but we consider
yt = β 1 + β2 x2t + t , wage education (1.2)
(i) If x3t is some variable which is not directly correlated with x2t and ut . Find the OLS estimator of 2 discuss on its consistency.
(ii) If x3t is an academic performance measure of individual t, which is expected to be correlated with x2t . Discuss on potential issues of the OLS estimator obtained from (1.1). (iii) If x3t is an academic performance measure of individual t, which is expected to be correlated with x2t . Discuss on potential issues of the OLS estimator obtained from (1.1).
Suppose that the true model is
yt = β 1 + β2 x2t + ut, Cov(x2t, ut) = 0.
wage ability
2. But due to data availablity, you consider
yt = β 1 + β2 x2t + t ,
wage test score
where the test score is an incomplete measure of ability. In the case where β2 > 0, discuss on
the direction of bias of the OLS estimator.
2 Empirical application
We will consider the following regression models:
log wage education
Model 2: yt = β 1 + β2 x2t + β3 x3t + β4 x4t + ut ,
Instructions:
1. Compute the IV estimate of β2 from Model 1 using mother’s education as the IV.
- “ivreg” package in R can be used for this excercise (install.pacakges("ivreg"); library(ivreg))
- result = ivreg(wage∼educ|meduc); report=summary(result), where edu : education, meduc = mother’s education
- The result must be similar to
2,IV = 0.213. (2.1)
2. Compute the standard error of 2 from Model 1.
- report$coefficients can be used.
- The result must be similar to
E (
2,IV) = 0.174. (2.2)
3. Compute the IV estimate of β2 from Model 2 using mother’s education as the IV.
- result = ivreg(wage∼educ+exp+exp2 |meduc+exp+exp2); report=summary(result), where edu : education, meduc = mother’s education
- Note : The basic grammar is
ivreg(dependent variable ∼ all the variables in “X” | all the variables in “Z”),
and in the above, the vectors of ones in X and Z should be excluded.
- The result must be similar to
2,IV = 0.232. (2.3)
4. Compute the standard error of 2 from Model 2.
- report$coefficients can be used.
- The result must be similar to
E (
2,IV) = 0.174. (2.4)
5. I recommend you to directly compute the IV estimator and the standard error by constructing data matrix y , X and Z as in the lecture.
6. This computing exercise is not mandatory.