I'm not sure how many players you look at, but my code reads 100% of players in a universe. Here's test output of a fictonal league under the latest patch release, looking at power talent. The table below shows how many players of any particular age were in the universe during the time of the league (60 years, sim, I think). All settings were default, with scouts off. i measured the number of players who received talent increases and decreases in 20-point bands. So this data, for example, says that seven of 798 17-yo hitters received a talent increase of > 60 points during their 17 yo season.
You can figure the rest our yourself.
Code:
Power
Age 17 18 19 20 21 22 23 24
Hitters 798 900 825 1236 1632 1501 1332 1211
+60 7 5 13 12 6 4 0 1
+40 18 16 31 36 27 20 10 11
+20 54 66 72 93 82 67 49 30
PosDev 124 132 133 200 198 161 110 74
None 436 558 503 776 1106 1054 972 890
NegDev 238 210 189 260 328 286 250 247
-20 88 73 78 91 115 102 83 66
-40 26 19 20 25 22 15 25 17
-60 8 6 6 4 6 4 3 1