Questions tagged [2sls]
Two-stage least squares is a regression technique from econometrics used in instrumental variables analysis.
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How to interpret the tests for weak instrument in R?
Stock & Yogo (2005) provide the rule-of-thumb that the first-stage F-test of an IV regression should be above 10 for the bias of the instrument to be less than 10%, and suggest to call weak an ...
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6 views
Why ivmodelFormula and ivmodel give different results in R?
I stumbled upon an issue with the ivmodel package: when exogenous covariates are included in the model, the ivmodel function ...
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13 views
2SLS in Fuzzy Regression Discontinuity
What is the logic of conducting an IV-2SLS in Fuzzy Regression Discontinuity Design?
Why can't we run a regression just like in Sharp RD?
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16 views
Interpreting the relationship between my instrumented variable (X1), X2, and Y (IV regression)
I have run an IV regression with a dichotomous outcome (Y) and my endogenous ("instrumented") regressor (X1) is also dichotomous. I am assessing whether continuous variable (X2) is moderating the ...
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10 views
Instrumental variables and GARCH
Can you use the predicted value from the first stage (as estimated using 2SLS) to replace the endogenous variable in a GARCH model? Or, what would be a different way of using instrumental variables in ...
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1answer
25 views
Is the IV approach applicable to endogenous count variable in a linear regression?
In a linear regression setting, one of the regressors (independent variables) is endogeneous. However, strictly speaking it is not continouus, but a count variable. A continouus instrumental variable ...
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28 views
Overidentified vs just identified models
Why go with overidentified models as opposed to just-identified?
If you can go with over-identified models, how many instrumental variables can you have at max in a 2SLS model?
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31 views
2sls asssumptions vs IV assumptions
Silly question but I was confused about the independence assumption for instrumental variables when they are used in 2SLS. Is it the case that the instrumental variable used in 2SLS only has to be as ...
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24 views
2SLS - With the same X's and Z's but 3 different Y's, Over-identification and Hausman tests give different results
Dear Stack Exchange users,
Let's say that my independent variable of interest is expected to be endogenous and that I want to investigate its effect on 3 separate outcomes.
I run separate 2SLS's (one ...
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1answer
49 views
Why the representation in the form of $Z'X(X'X)^{-1}X'Z$ can not be simplified into $Z'Z$
Representation similar to $Z'X(X'X)^{-1}X'Z$ frequently appear to e.g. 2SLS.
I think that $Z'X(X'X)^{-1}X'Z = Z'XX^{-1}X'^{-1}X'Z = Z'(XX^{-1})(X'^{-1}X')Z = Z'Z$. So why it seems that in the context ...
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1answer
64 views
Standard errors of *partial* two stage least squares coefficients
Here partial 2SLS (I coined this term and found it descriptive) is the approach that SAS uses for 2SLS. Compared to "ordinary" 2SLS which in the first stage projects all explanatory variables $X$ onto ...
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25 views
Interpretation of correlation in endogenous regression model
Suppose you have a linear regression with an endogenous regressor $x$ that can be represented as follows:
$x = z'\delta + \epsilon_1$
$y = \beta x + w'\gamma + \epsilon_2$
where
$\begin{pmatrix}\...
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1answer
51 views
Instrumental variables with non-normal endogenous
Does it make sense to conduct an instrumental variables model where the endogenous variable of interest is continuous but not normally distributed? I know for normal regression purposes, there is no ...
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55 views
Role of rank condition in identification of 2SLS - matrix algebra
I could write down all the steps for identification of the 2SLS estimator but my question is really a matrix algebra question which is required in the last step for finding out what the beta vector is ...
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1answer
59 views
How should an author convince readers that weak instruments are not a problem?
I see in a lot of instrumental variables papers that authors will often discuss first stage $R^2$ values or $F$ statistics to assuage concerns that they are working with a weak instrument. This seems ...
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160 views
2SLS overidentification test - Why is it the test only helps deciding if the added IV is endogenous? And why adjust for d.o.f?
I heard from a lecture that if we test for overidentification, the output will only help us to determine whether the added IV is exogenous. It however won't help in telling, and in fact we can never ...
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17 views
Second stage in TS2SLS
I am working with a Two Stages Two Steps Least Squares (TS2SLS) in a Diff-in-Diff context, with cross-section data. I have a large sample where I observe the binary outcome Y as well as the ...
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42 views
IV: Can I use different samples in first and second stages?
I want to run an IV regression, where in the first stage I use different sample (size) compared to the second stage. The approximate logic is as follows. I want to study how trading volume affects ...
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313 views
Endogeneity bias in cross sectional data
My supervisor asked to use 2SLS in thesis titled : Does Women's Autonomy affect child health survival" I used stata and found women's autonomy as endogenous variable, while women's education was ...
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13 views
Help with ordinal variables
In my research, I am trying to evaluate the effect of the income drop (during a recent economic crisis) on general trust levels in the country. The variable that describes trust is an ordinal variable ...
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2answers
456 views
How does IV 2SLS obtain a causal coefficient?
Despite reading and conducting several practical examples with IV 2SLS, I am still uncertain how, specifically and mathematically, 2SLS is able to obtain a causal coefficient, β, of an assumed ...
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18 views
Why do we need to reduce the amount of IV’s in case of overidentification?
In an IV regression model, we may have more instrumental variables $Z$ than explanatory variables $X$. In this case, the identification equation is still
$$E(z_iy_i)=E(z_ix_i)\beta=A\beta$$
But now, ...
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596 views
2SLS Estimation for a Fuzzy Regression Discontinuity Design
I am using a Fuzzy Regression Discontinuity Design for the first time and this maybe a very basic question to some. I am estimating the Fuzzy RD with 2SLS.
Suppose, my data is of the following form:
...
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128 views
2SLS (IV) with fractional outcome variable and spatially autocorrelated error terms
I face the challenge of estimating a 2SLS (IV) model with a fractional (ranging between 0 and 1) outcome variable and spatially autocorrelated error terms (the data is spatially explicit, i.e. for ...
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1answer
34 views
mediate() vs lavaan, missing path coefficients, 2SLS does not resolve
Doing a straightforward mediation analysis, a => b => c (indirect effect) and a => c (direct effect).
If I do this in mediation::mediate(), I get
...
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1answer
85 views
2sls - instrumental variables mean and variance of exogenous variable
I do not usually use two-stage-least-square regression technique and I am not a theoretic of econometrics; thus, I hope you will pardon me for this (possibly) clumsy post.
Introduction
Let's start ...
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1answer
300 views
why is 2SLS with dummys the same as GLS on group means?
I'm reading Mostly Harmless Econometrics (Available here), and on page 100 they say that 2SLS with dummy instruments is the same as GLS on a set of group means. I don't understand why. From the ...
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1answer
597 views
What do the assumptions for 2SLS (two-stage least squares) mean in the context of instrumental variables?
The assumptions for 2SLS are (z are the vector for instrumental variables; x are the explanatory variables in the model; u are the vector for the error term):
Assumption 2SLS.1: E(z'u)=0,
Assumption ...
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1answer
1k views
Endogeneity problem in OLS
I have an OLS-model with about 30 predictor variables, from which I got both big endogeneity and heteroscedasticity problems. The variables reporting these problems also pop up in the check for ...
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136 views
Significant Predictor with a Negative Adjusted R-Squared Value: Instrumental Variables Regression
I'm running an instrumental variables regression with a single predictor on a sample size of 120.
When I run the regression, the predictor is significant at the 0.01 level, but the adjusted R-squared ...
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1answer
438 views
Is Sargan-Hansen J test relevant for panel data containing large number of observations?
I am working on a project that has 4680 observations (18 years, 265 regions), in which one variable is endogenous. We tried various combinations of two IVs, but always end up with a significant Sargan-...
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19 views
Why functional specification is important in RDD setting?
I'm reading Clark(2009) paper regarding the impact of education reform on school performance. The rule is that the school initiated a democratic vote at first and if 50% of students vote in favor of ...
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240 views
Simultaneous equations with interaction terms
How do you estimate the following simultaneous equation model on a panel dataset?
$Y_1=\beta_1X_1Y_2 +\beta_2X_2+e_1$
$Y_2=\alpha_1X_1Y_1 +\alpha_2 X_3+e_2$
$Y_1$ and $Y_2$ are endogenous while $...
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1answer
520 views
Why use two stage least squares for the instrumental variable estimator?
Following the rationale from Econometric Methods with Applications in Business and Economics by Heij et al., the instrumental variables estimator $b_{IV}$ for the linear regression model
$y = X\beta ...
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142 views
Should instruments always weakly increase standard errors?
In OLS, are standard error estimates using some instrument $z$, different from $x$ always weakly larger than standard errors when not using instruments? This has been discussed before: Why is the ...
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205 views
Nonlinear Two Stage Least Squares Instrumental Variable method
I am trying to figure out how this paper estimates extended Solow production function using nonlinear two stage least squares instrumental variable method (or non linear 2SLSIV).
The full ...
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1answer
54 views
Continuous instrument- 2SLS estimation
I am trying to estimate the enrollment premium at high-fees schools i.e., impact of high-fee school enrollment on learning outcomes. I am instrumenting high-fee school enrollment by using a continuous ...
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484 views
Fuzzy RDD in Stata with two cutoff points
I am running a Fuzzy Regression Discontinuity Design using 2SLS.
If I specified the model (and most importantly the IVs) correctly as i have never worked on a RDD before. The difference to the usual ...
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1answer
497 views
Is it possible to do a 2sls with linear regression in the 1st stage and logistic regression in the 2nd stage?
I'm working on a a bivariate logistic regression. But I have an endogeneity problem and I want solve it through 2sls with 2 instrumental variables.
My thought was to regress (OLS) in first stage and ...
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94 views
2sls with lagged dependent
I have seen many papers using dynamic panel regressions when the lagged dependent is a regressor and the data has the standard panel format. so,
y(t)=constant + beta1*y(t-1)+ beta2*X(t)
is often ...
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1answer
535 views
Bivariate probit versus 2SLS, contradictory results (sign)
I am currently facing puzzle and I hope some of you will be able to provide me some insights. I have this model: y: binary variable, x1: binary variable (endogenous), z: binary instrument, x2: ...
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21 views
two models in 2sls procedure
I am trying to do following.
bysort Country: regress bdr fam MTB lnTA
this is my first stage regression for second stage I want to use another variable std as my dependent variable and use predicted ...
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240 views
Interpreting dummy variable in Heckman 2SLS
My question is regarding interpreting the output of a Heckman 2SLS.
Background information: I am exploring how institutional investor presence affects investments and firm performance during ...
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1answer
240 views
Heterogeneous treatment effects with 2SLS local average treatment effect (LATE)
I am interested in a strategy to calculate heterogeneous treatment effects with an IV strategy for local average treatment effects (LATE).
I am estimating the effect of postsecondary educational ...
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0answers
588 views
How to work out direction of omitted variable bias in 2sls
In OLS you can reason to the direction of omitted variable bias by using the following formula:
OVB = [Omitted in long] x [Relationship between omitted and variable of interest]
My question: is ...
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372 views
2SLS vs OLS Efficiency Question
I'm doing some studying for finals and I'm wondering what would happen in a case like this.
With the following model
$y_t = x_t * \beta + \epsilon_t$
Say you had two IV's, $a_t$ and $b_t$. In ...
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1answer
59 views
If my IV (denoted Z) equals 1, my endogenous var D always equals 1; is this a problem?
I have a binary instrumental variable Z={0,1} and a binary endogenous variable D={0,1}. By construction, D=1 necessarily holds if Z=1. There are also cases where D=1 if Z=0, but there are no cases ...
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1answer
328 views
Endogenous variable problem or why to use 2SLS?
Consider linear model $$y = \beta_0 + \beta_1x_1 + \dots + \beta_{k-1}x_{k-1} + \beta_kx_k + u $$ where $x_k$ is correlated with $u$ which results into inconsistent estimators of $\beta$.
As I ...
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1answer
344 views
How does an IV regression/2SLS affect coefficient (increase/decrease) with initial simultaneity?
So let's say I want to look at how X affects Y, but there is some simultaneity going on: X ...
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1answer
481 views
Linear first stage, non-linear second stage 2SLS regression
I was wondering if it's possible to perform a 2SLS regression where I first run a regression for my endogenous variable, obtain the predicted values and then use them in my second stage regression (a ...
