110 likes | 208 Views
More advanced techniques. & A quick look at POLS 603. Simultaneous Equations. There are times when we are unsure of causation Consider the following hypotheses Presidents use military force intentionally to boost their popularity
E N D
More advanced techniques & A quick look at POLS 603
Simultaneous Equations • There are times when we are unsure of causation • Consider the following hypotheses • Presidents use military force intentionally to boost their popularity • When popularity is high, presidents are les restrained in their decisions to use force • Does use of force cause changes in popularity, or do changes in popularity cause presidents to elect the use of force?
A Model of Presidential Popularity • So: • Note that since Use of Force is related to ut, and Popularity is related to et, there are correlated errors. • We sometimes refer to this as an endogeneity problem.
Variable types • This leads us to classify the variables in a model as one of three types: • Endogenous variables – those that are determined within the model structure. The dependent variable is endogenous. • Exogenous variables – those that are determined outside the model. The independent variables are exogenous. • Lagged endogenous variables, which are often treated as exogenous variables due to their prior causation.
Simultaneous Causation • Because of our prior hypotheses, we can infer that Presidential Popularity and the decision to use Military Force cause each other. • They are simultaneously determined. • For a sociologist, this is a non-recursive model.
Conditions to estimate Simultaneous models • In order to estimate such a model, we have to satisfy certain conditions, which we call Identification: • Order Condition: In order for an equation to be identified, it must exclude at least M-1 variables. • Just Identified • Over identified • Rank Condition: An equation is identified if and only if at least one non-zero determinant of order (M-1)(M-1) can be constructed from the coefficients of the variables excluded from that equation.
Methods of estimation • 2 Stage Least Squares (2SLS) • 3SLS • FIML
Uses • Macroeconomic models of the economy. • Sometimes, thousands of equations.
POLS 603 • Easier course than 602 • Readings harder in that they are more complex models, with more complex math • Expectations about math are less • Requirements • Take home final with general comp style questions • Paper using 1 advanced method
Topics for 603 • Matrix Algebra • Time Series • Univariate • Multivariate • Polled Cross sectional time series • Vector Autoregression • Others
Event History analysis • Duration • Survival • Count Models • Social Network Analysis • Bootstrapping • Computational Models (AI)