Supreme Splits Part 2: Player Age

Check out the 2011 batting splits by player age:

Split	G	GS	PA	AB	H	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	BAbip
Ages 25-	14218	1177	44137	39638	10004	1979	285	1029	4487	880	322	3395	8886	.252	.315	.395	.710	.299
Ages 26-30	27251	2151	82534	73644	19088	3851	429	2119	8992	1711	638	6881	15258	.259	.326	.409	.736	.299
Ages 31-35	15219	1241	47523	42514	10663	2103	149	1178	5164	547	243	3893	8599	.251	.317	.390	.708	.287
Ages 36+	3692	287	11024	9909	2512	466	35	226	1163	141	58	849	1745	.254	.314	.376	.690	.285

Provided by Baseball-Reference.com: View Original Table
Generated 11/21/2011.

Tons of interesting stuff here...

It's well known that most players peak between age 27 and age 29, and the data backs that up. Note that BA, OBP, and SLG are all higher for players between 26 and 30 than for any other group.

On a per-plate-appearance basis, the Age 26-30 group also leads in doubles, homers, stolen bases (and CS), and walk. Players 25 and under lead in triples and strikeouts.

Notice how BAbip drops as players get older--I'm guessing that's an effect of fewer infield hits as players slow down a bit with age.

Game starts--44.3% of them were made by that Age 26-30 group. The youngsters started 24.2% while the 31-35 year olds started 25.6%. The oldest group started just 5.9% of the games.

Oh my how things have changed. At the height of the Steroids Era in 2001, look at the same breakdown:

Split	G	GS	PA	AB	H	2B	3B	HR	RBI	SB	CS	BB	SO	BA	OBP	SLG	OPS	BAbip
Ages 25-	12113	1074	39768	35735	9197	1812	242	993	4283	809	324	2925	7234	.257	.318	.405	.723	.295
Ages 26-30	26557	2067	80776	72002	19360	3949	398	2428	9702	1437	668	6658	13791	.269	.336	.436	.772	.300
Ages 31-35	16578	1329	50929	45008	11854	2360	224	1540	6224	637	336	4555	8707	.263	.335	.428	.763	.293
Ages 36+	5329	386	15488	13489	3468	692	64	497	1879	220	80	1668	2672	.257	.342	.428	.771	.285

Provided by Baseball-Reference.com: View Original Table
Generated 11/21/2011.

Suddenly there's much less of a gap between that leading group (Age 26-30) and all the older players. In fact, The oldest group has nearly the same OPS as the 26-30 guys. It's the really young guys who performed well below other folks.

And check out how the game starts break out.

Only 42.6% were started by the Age 26-30 group (as compared to 44.3% in 2011). The youngsters started 22.1%, the 31-35 year olds started 27.4% and the 36+ group started 7.9%.

In 2001, players 31 and older started 35.3% of the games, but in 2011 that number was down to 31.5%. You probably won't find any better statistical proof that use of banned substances extended careers.