Human capital could also be applied to topics beyond returns to individuals from education.
The idea was a powerful variable in explaining why some countries fared far better than others: to promote income growth over many years, heavy investment in schooling was necessary.
It shed light on why firms in poor countries tended to be more paternalistic, providing dormitories and canteens: they reaped immediate productivity gains from rested, well-fed workers.
It informed big increases in the numbers of women studying law, finance and science since the 1950s: the automation of much household work meant that women could invest more in building their careers.
And it helped explain the shrinkage of families in wealthy countries: if increasing value is placed on human capital, parents must invest more in each child, making large families costly.
But any theory that attempts to explain so much is bound to encounter pushback.
Many critics bristled at Becker's market-driven logic, which seemed to reduce people to cold, calculating machines.
Although “human capital” is an unsightly term—in 2004 a panel of German linguists deemed Humankapital the most offensive word of the year—it is the task of social science to identify and refine concepts that would otherwise be fuzzy.
It took Becker's framework to make the importance of education explicit, and to put people at the heart of economics.
Within the discipline, some objected that Becker had overstated the importance of learning.
Education matters not because it imparts knowledge, critics said, but because of what it signals about the people who complete university, namely that they are disciplined and more likely to be productive workers.
In any case, people of greater abilities are the ones who are most likely to get higher degrees in the first place.
Yet increasingly sophisticated empirical analyses has revealed that the acquisition of knowledge is in fact a big part of what it means to be a student.