Consider the fitting of the following model: Y = 0 + 1X1 + 2X2 + 3X3 +

Consider the fitting of the following model:
Y = β0 + β1X1 + β2X2 + β3X3 + ε
where
Y = tax revenues as a percentage of gross national product in a country
X1 = exports as a percentage of gross national product in the country
X2 = income per capita in the country
X3 = dummy variable taking the value 1 if the country participates in some form of
economic integration, 0 otherwise
This provides a means of allowing for the effects on tax revenue of participation in some form of economic integration. Another possibility would be to estimate the regression
Y = β0 + β1X1 + β2X2 + ε
separately for countries that did and did not participate in some form of economic integration. Explain how these approaches to the problem differ.