Between 1970 and 2000, the proportion of people graduating with a high school diploma in the US increased from 50% to 80%. There was a marked increase in economic growth during this time period. What is this an example of? Select one answer. G O It is an example of public investment. which increased the supply of workers in the US. O It is an example of an increase in human capital, which weakens the law of diminishing returns. O It is an example of capital deepening because more physical capital was invested in schools. It is an example of an increase in human capital, which increases the productivity of workers. It is an example of the labour force increasing because people could find jobs more easily.