One way to think of it is like this- in the olden days how much work you accomplished in a day was mostly a function of your level of effort. If you put in a solid 10 hour day in the fields you'd accomplish 25% more than somebody who put in 8 hours more often than not. But as technology has advanced, the productivity of a farmer has steadily had more and more to do with how smart they work. Maybe they will be 40% more productive if they make the right call about making a particular adjustment to the mix of fertilizer they use and the farmer that works 8 hours might dramatically outperform the farmer that works 10 hours if he is making smarter decisions. That's true in every field. Accountants used to be mostly measured by the amount of time they put in tabulating columns of numbers and re-checking it, but now all that is done by computers and they are mostly measured by strategic decisions they make. Computers and machines are steadily shifting more and more of the emphasis in most fields to how smart people work more than how hard they work. A database engineer might be at his most productive spending a whole month researching a particular setting in the database and only making one minor tweak. The same thing plays out on the larger scale. A worker might be more productive spending 10 years preparing to work as smartly as possible and 30 years working than they would be if they just spent 40 years working. As time goes on that ratio will keep skewing more and more that way. For example, we will reach a point where the only human involvement in farming is programming various machines. If the last guy studied how to optimize that programming for 20 years, the odds are that you'll need to study it for 21 years to be able to improve on it.