《计量经济学导论》ch1616页PPT

Income per capita
„Behavioral equation“ of city government
(= observed equilibrium outcomes in each county)
Simultaneous equations model (SEM):
Note: Without separate exogenous variables in each equation, the two equations could never be distiguished/separately identified
Simultaneous Equations Systems
Example: Murder rates and the size of the police force
„Behavioral equation“ of murderer population
Murders per capita
Police officers per capita
Simultaneous Equations Syห้องสมุดไป่ตู้tems
Example: Labor demand and supply in agriculture (cont.)
Competition on the labor market in each county i will lead to a county wage wi so that the total number of hours his supplied by workers in this county equals the total number of hours hid demanded by agricultural employers in this county:
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Observed supply shifters e.g. manufacturing wage
Unobserved supply shifters e.g. immigration flows
Unobserved demand shifters e.g. food market shocks
Observed demand shifters e.g. agricultural land area
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Structural error terms (uncorrelated with the exogenous variables)
Endogenous variables Exogenous variables
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Simultaneous Equations Systems
Example: Labor demand and supply in agriculture
Annual hours supplied by workers in a given county if the average hourly wage offered to such workers is w
Annual hours demanded by employers in a given county if the average hourly wage paid to workers is w
Wage elasticity of supply
Wage elasticity of demand
Simultaneous Equations Systems
Simultaneity is another important form of endogeneity Simultaneity occurs if at least two variables are jointly determined A typical case is when oberved outcomes are the result of separate behavioral mechanisms that are coordinated in an equilibrium The prototypical case is a system of demand and supply equations: • D(p) = how high would demand be if the price was set to p? • S(p) = how high would supply be if the price was set to p? • Both mechanisms have a ceteris paribus interpretation • Observed quantity and price will be determined in equilibrium Simultaneous equations systems can be estimated by 2SLS/IV