Questions tagged [2sls]

Two-stage least squares is a regression technique from econometrics used in instrumental variables analysis.

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1answer
14 views

Why is the Wald Estimator equal to LATE (binary instrument)?

In Mostly Harmless Econometrics, Equation (4.1.12) states that in IV setting with binary instrument $Z$, treatment $D$, and potential outcomes $Y_1,Y_0$ for $Y$, then $$E[Y_1-Y_0|D_1 = 1, D_{0} = 0] =...
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21 views

Using residuals in 2SLS regression to remove reverse causality

Someone suggested the following idea to me to control for reverse causality. Suppose we want to test for the effect of $X$ on $Y$ in a panel data set, but we suspect that there is reverse causality. ...
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1answer
25 views

Test for weak instruments in Stata when using VCE robust [closed]

does anyone know how I can test for weak instruments (one instrument, just identified model) after 2SLS regression in Stata when using robust standard errors (VCE robust)?
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1answer
112 views

A 2SLS when the instrumented variable has two interactions in the model

I am using ivreg and ivmodel in R to apply a 2SLS. I would like to instrument one variable, ...
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1answer
797 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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1answer
135 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
166 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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7 views

How to properly use IV regression when my endogenous variable is a ratio?

I’m trying to better understand the issues relevant to the selection of an instrumental variable for a project I’m working on (and also more generally). In a recent example I ran into, my endogenous ...
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11 views

Inconsistency of Forbidden Regression Estimator

I am trying to prove the inconsistency of the estimator of the in the following model: 1st stage: 2nd stage: When the population model is and . I know this is a forbidden regression because ...
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14 views

Instrumental variables: Fixed effects only in the second stage?

I have been under the impression that for a 2SLS FE model you got to have the fixed effects in both stages. So if you have a time invariant instrument you can forget about your FE, as they already ...
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1answer
5k views

2SLS with endogenous interaction term

I am trying to estimate a peer effects model where a certain characteristic of the individual and the peers might be endogenous: $$\ y_i=\alpha + \beta_1 Controls_i + \gamma_1 Endog_i +\gamma_2 \...
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9 views

Social-Network Peer Effect Regression

I have locally transformed model from Bramoullé 2009 to be estimated for regression estimation $\begin{equation} ( \mathrm{{I}} - {G}_{l}^{*}){y}_{l} = \beta_2( \mathrm{{I}} - {G}_{l}^{*}) {G}_{l}^...
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14 views

Addressing Near Perfect Correlations In Highly Competitive Commodity Markets

I am working on an analysis for a highly competitive agriculture market. I'm looking at county elevators in Iowa where competitors set their price for tomorrow's corn "ask" the evening before, but ...
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1answer
43 views

Missing R squared value from STATA output, what does that mean?

I ran a 2SLS regression in STATA, and there is no R squared value given in the output (only a dot where the value should be). What could this be interpreted as? Is it missing because it may be a ...
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34 views

How do I tell if my Instrument is valid?

I have the following structural model (similar) which I wish to estimate $$ Y_t = \beta_0 + \beta_1 X_t + \epsilon_t $$ but I'm aware that $X_t$ is endogenous or equivalently, $E[X_t\epsilon_t]\ne 0$....
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16 views

Simplifying last step of IV estimator derivation with matrices

I've been reading about IV in this textbook. On page 39 (page 5 of the PDF), I'm confused by the last step. How does [(z'z)^(-1)z'y]/[(z'z)^(-1)z'x] simplify to (z'x)^(-1)z'y? I can see that the (...
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1answer
518 views

What control variables do we need for IV regression?

I am running and IV regression and I need help on what control variables to include in the IV regression. I believe that I have to control for potential variable that are correlated with both the ...
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10 views

Estimating post treatment outcome of IV

In the Angrist, Mastering metrices book (page 118, chapter 3, Instrumental variable) Angrist calculated "recidivism was greater among suspects assigned to be coddled than among those assigned to be ...
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59 views

Why do estimates differ so much between Instrumental Variable (ivreg) vs 2SLS (lm)?

I am working with some messy pilot data to figure out whether Instrumental Variable analysis will help interpret the results of a randomized controlled trial I am preparing. Treatment compliance in ...
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26 views

Interpretation of Hausman test - IV models

I ran two IV models: 1) ivreg 2sls y x1 (x2=z1) 2) ivreg 2sls y x1 (x2=z1 z2) than I did a Hausman test, and it was not significant, so I could not reject the null. What does that mean? Is z2 a valid ...
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7k views

Weak first stage in 2SLS

I have a simple IV model with 1D variables: $N = \alpha_z + \beta_z Z + \epsilon_z$ $S = \alpha_s + \beta_s N + \epsilon_s$ $N$ is an integer, while $S$ is dummy. $Z$ is by construction ...
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11 views

How to decide which variables belong in the first and second stage of the 2SLS method

Let's assume I want to estimate the model: Income = Education + Gender + u Let's say I would like to use the occurrence of two events with ...
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1answer
2k views

Can there be endogeneity?

I am performing a regression in which I suspect there could be endogeneity between the main explanatory variable and the dependent. As a first step I perform an OLS regression and then, to control for ...
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1answer
263 views

Are There Evaluation Criteria For Instrumental Variables?

If theory points to multiple possible instruments that can be used, how can I choose which one of them is the best for 2SLS? I read that good instrument should be significant and correlated with the ...
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15 views

How apply 2SLS in order to find estimates of the SEM's model , provided that the lag values of the variables are used?

How should I apply 2SLS in order to find estimates of the model of a system of simultaneous equations, provided that the lag values of the variables are used? For example, there is the following ...
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141 views

Instrumental variables with interactions between endogenous variables

I have two endogenous variables $x_1$ and $x_2$ and am trying to estimate the following model: $$y = \theta_0 + \theta_1 x_1 + \theta_2 x_2 + \theta_{12} x_{12}$$ where $x_{12} = x_1\times x_2$. I'm ...
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24 views

Explaining instrumental variable 2SLS in a simple yet precise way

I am trying to explain IV 2SLS in a non-technical yet precise way. However, I still think I can improve, and I would highly appreciate input that could make some points clearer. One of the sticking ...
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19 views

Implementation of 2SLS in regression with AR errors?

Consider the following simple example: $Y_t=\beta X_{t-1}+\varepsilon_t$ $X_t=\gamma Y_t + Z_t +u$, where $\varepsilon_t=\alpha\varepsilon_{t-1}+\eta$, and $E[Z_t\varepsilon_t']=E[uu']=E[\eta\...
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1answer
317 views

2SLS for sales data (problem with IV)

I am given a task to perform an analysis on marketing data and to find out if the prices for the products and marketing budget are set correctly. In order to do it, I need to find a suitable model ...
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39 views

PCA of many weak IVs in 2SLS

"Instrumental variable estimators can be severely biased in finite samples when the degree of overidentification is high or when the instruments are weakly correlated with the endogenous regressors." ...
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2answers
3k views

Why do you put all the exogenous variables into the first and second stage of 2SLS?

For a general MLR, let's say we have k endogenous X's, r exogenous W's, and m instruments. The first stage of the 2SLS model is regressing each of the endogenous X's on all the Z's and W's. For the ...
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48k views

Two stage models: Difference between Heckman models (to deal with sample selection) and Instrumental variables (to deal with endogenity)

I am trying to get my head around the difference between sample selection and endogeneity and in turn how Heckman models (to deal with sample selection) differ from instrumental variable regressions (...
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90 views

Meaning of centred and uncentered r square [closed]

I'm not sure I understand fully the meaning of centred/uncentered r2. Is uncentered r2 is same as adjusted r2? and if not, how can I know the adjusted r2? That result estimated by IV analysis. the ...
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1answer
800 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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37 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
58 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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1answer
14k views

Basic 2SLS IV Questions in Stata

(1) If I believe my instrument is exogenous conditional upon a few exogenous variables, do I include them only in the first stage? I.e. would the command be: ...
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92 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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1answer
377 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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63 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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1answer
66 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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36 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
129 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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0answers
102 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
89 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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137 views

Multiple (binary) endogenous variable for separated subgroups

I want to specify an empirical model of home ownership like: \begin{align} Y &= X'\beta+\sum_j \delta\cdot D_j + \gamma_1\cdot\lambda(X_1\cdot\theta)+\text{city_dummies}+u \\ D_j &= \phi_j\...
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1answer
4k views

2SLS but second stage Probit

I am trying to use instrumental variables analysis to infer causality with observational data. I have come across a two-stage least squares (2SLS) regression which is likely to address the ...
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2answers
961 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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0answers
1k 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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169 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 ...