Value and outcomes
Diminishing returns
Each extra unit of effort adds less value than the one before. The tenth hour of research in a week teaches you less than the first.
Most design activities follow this curve. The first round of usability testing finds the big problems; the fifth mostly finds small ones. The first component in a library saves a lot; the hundredth saves a little.
It is the reason balanced teams outperform lopsided ones. Pouring all capacity into one activity maxes nothing, because the extra effort is worth less and the neglected activities stop contributing at all.