The OLS slope estimator is not defined if there is no variation in the data for the explanatory variable. You are interested in estimating a regression relating earnings to years of schooling. Imagine that you had collected data on earnings for different individuals, but that all these individuals had completed a college education (16 years of education). Sketch what the data would look like and explain intuitively why the OLS coefficient does not exist in this situation.

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The Answer of The OLS slope estimator is not defined if there is no variation in the data for the explanatory variable. You are interested in estimating a regression relating earnings to years of schooling. Imagine that you had collected data on earnings for different individuals, but that all these individuals had completed a college education (16 years of education). Sketch what the data would look like and explain intuitively why the OLS coefficient does not exist in this situation.

The OLS Slope Estimator Is Not Defined If There Is