I created the 2015 year end ranking of WTA players by their birth year with top 10 for each year. This year I didn't create intermediate list at 2-3 other times throughout the year so there's quite a bit of change between now and the last time I did the list - 2014 year end. At right there is a link to the 2015 top 10 by birth year page as well as other year end lists.
There are 28 new players in the top 100 when compared to last year. Players moving from outside of the '14 top 100 into the '15 top 50 were #36 Gavrilova, #44 van Uytvanck, #46 Pereira, and #48 Konta. Players from the '14 top 50 that dropped out of the '15 top 100 were the injured Peng and Dellacqua.
There were a few years where the #1 player born in year X changed. Former '86 #1 Peng missed almost the entire year with injury and was replaced by Strycova. The miserable season by Bouchard dropped her from #1 to #5 among those born in '94 and Svitolina took over the top spot after a nice season. In '96 Vekic surrendered her top spot to Siniakova by one ranking spot.
Speaking of '96, a slump by Vekic after a promising start to her career leaves '96 lacking when compared to '95 and '97. Both those years have 4 top 100 players (Keys, Witthoeft, Putintseva, Kontaveit & Bencic, Kasatkina, Konjuh, Ostapenko).
'87 continues to be a banner for women's tennis but with their aging they've been brought back to field a bit and the depth in the top 50 is not what is once was. However, they still have 5 top 25 players: Sharapova, Safarova, Ivanovic, Errani, and Petkovic. '92 continues to lag behind with just 5 top 100 players but we'll see if that depth improves behind Pliskova, Watson, McHale, Arruabarrena, and Linette.
I'll let you look through the page for more observations. Way down the list apparently Patty Schnyder has come out of retirement and is ranked #746.