Okay... more like, Joe can get done in a day what would take Jim a week.. or Joe can do more in a month, than Jim could do in a year. Perhaps the exponent is a bit off.. but more than cumulative output was implied.

A lot of this coming from being able to expect/plan for future enhancements/changes than the one-off output. My own personal reference with this comes from managing several projects with local and overseas teams with varying degrees of experience.