Concept of overkill
If the next step in your research is one turn away it is possible to decrees the percentage of gold spent on research without subsequent relative decreasement of the amount of turns to the next step in research. Thus creating an extra amount of gold in your treasury.
This effect is explained as you think of it as compensation for overkill research. I refer to the amount of lost research (79) caused by the difference between needed points for the next step (1) and actually produced in the current step (80).
The same overkill effect applies to production. These production losses can be reduced by good production management, e.g. at a given production level in a city there is less loss if you choose to produce artillery in 2 turns in stead of a tank in 3 turns, while another city's production level produces both tank and artillery in 3 turns.
