# Population Regression Model

Learn how to create the underlying population regression model for the Braithwaite study.

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The underlying population regression model, motivated by the preceding theoretical expectations, isn’t explicitly specified by Braithwaite but can be easily specified as follows:

$Spread = \beta_0 + \beta_1 Territory+\beta_2 Resources+\beta_3Mountain+\beta_4 Forrest+ \beta_5Ocean$

$+ \beta_6 Size\ of\ States+\beta_7 VitalBorder+\beta_8 Control.variable+ \epsilon$

According to Braithwaite, the dependent variable, $spread$, is a circular area measured in squared kilometers, log transformed. The key independent and control variables are on the right-hand side, with all the $\beta_s$ indicating the marginal effects of respective right-hand side variables. Drawn from the article, the key independent variables, their measurements, and expected effects are as follows in the table below.

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