You want to estimate the effect of years of education on earnings

Education is the foundation of any society and though education effects lots of things, the impact of education can be evaluated by the total years spent in attaining education by the person and contribution of the person to the GDP of the country.

An empirical investigation can be made by collecting the data of, let say, 2005-10. Then, an empirical study should be made on the level of the income earned by the people in the year 2015, if they have finished their education in the year 2005. Similarly, data should be collected on what level of income people are earning in the year 2020, if they have finished their education in the year 2010. The education level of people should be studied and accordingly the data on their contribution to GDP should be assessed. After collecting the data, one could statistical measures like regression analysis in order to check the impact of education on earnings of the people.