To illustrate a bit better, lets consider an item which has a baseline of 200 hours.
Workers -> Time to complete
The current algorithm (basically a linear function) produces time to complete as follows:
1 -> 380 hrs, 2 -> 360hrs, 3 -> 340hrs, 4->320hrs...
8 ->240hrs, 9->220hrs, 10 -> 200hrs, 11 -> 180hrs, 12 -> 160hrs...
16 -> 80hrs, 17 -> 60hrs, 18 -> 40hrs, 19 -> 20hrs, 20+ -> 1hr
Inverse proportional would go like this:
1 -> 2000hrs, 2 -> 1000hrs, 3 -> 667hrs, 4 -> 500hrs, 5 -> 400hrs...
8 -> 250hrs, 9 -> 222 hrs, 10 -> 200hrs, 11 -> 182hrs, 12 -> 167hrs...
16 -> 125hrs, 17 -> 118hrs, 18 -> 111hrs, 19 -> 105hrs, 20 -> 100hrs...
30 -> 67hrs, 40 -> 50hrs, 50 -> 40hrs, 60 -> 33hrs
Diminishing returns would go something like this (at 0.9 Pf):
1 -> 1303hrs, 2 -> 686hrs, 3 ->481hrs, 4 -> 379hrs, 5 -> 318hrs...
8 -> 229hrs, 9 -> 213hrs, 10 -> 200hrs, 11 -> 189hrs, 12 -> 181hrs...
16 -> 159hrs, 17 -> 156hrs, 18 -> 153hrs, 19 -> 151hrs, 20 -> 148hrs...
30 -> 136hrs, 40 -> 132hrs, 50 -> 131 hrs, 60 -> 130hrs