Average Age Of The Best Players Over Five Year Periods Since 1947

Using the Baseball Reference Play Index, I found the top 10 and top 25 players in WAR for 5-year time periods starting in 1947. So 1947-51 was the first period. Then 1952-56 and so on. The table below shows these averages. The WAvg columns are the average age weighted by WAR. The two lowest averages for the top 10 were the 1957-61 periods and the 1977-81 periods.

Years	Top 10 Avg	Top 25 Avg	Top 10 WAvg	Top 25 WAvg
1947-51	30.5	29.64	30.15	29.63
1952-56	27.6	29.28	27.33	28.9
1957-61	26.6	27.62	26.59	27.25
1962-66	28.4	27.38	28.72	27.66
1967-71	29.6	28.76	29.9	29.02
1972-76	27.6	28.12	27.68	28.08
1977-81	26.1	27.56	26.25	27.48
1982-86	27.6	28	27.52	27.88
1987-91	29.1	28.32	28.97	28.38
1992-96	27.1	27.92	27.06	27.8
1997-2001	28.1	28.44	28.16	28.46
2002-06	29.8	29.56	29.8	29.74
2007-11	27.85	27.7	27.98	27.75
2012-16	27.12	28.9	27.18	28.54

The good young players from 1957-1961 were

Player	WAR	Avg Age
Hank Aaron	41.3	25
Frank Robinson	30.9	23
Al Kaline	29	24
Rocky Colavito	23.4	25

The good young players from 1977-1981 were

Player	WAR	Avg Age
George Brett	34.3	26
Gary Carter	27.4	25
Andre Dawson	26.4	24
Keith Hernandez	24.9	25
Chet Lemon	24.7	24
Willie Randolph	24.6	24

 
 

This next table shows how many of the players in the top 10 and top 25 had an average age less than 27 in each period. That means 26 or less and would include guys who were 24-25-26-27-28, so at least 2 of their seasons were at age 25 or younger. 1977-81 had six "young" players in the top 10, the most for any period. 1952-56 is second with 5. Both 2007-11 and 2012-2016 have had a large number of young players in the top 25.

Years	Top 10 < 27	Top 25 < 27
1947-51	1	6
1952-56	5	3
1957-61	4	10
1962-66	3	11
1967-71	2	7
1972-76	4	8
1977-81	6	10
1982-86	4	9
1987-91	2	8
1992-96	4	8
1997-2001	3	7
2002-06	1	5
2007-11	4	11
2012-16	2	12

This time line chart shows how many players 25 or younger had a WAR of at least 5 per team each year going back to 1946 (I used 4.75 for 154 game seasons and made similar adjustments for strike years). I did it per team since when there are fewer teams, not as many players will reach a given WAR. Baseball Reference says a WAR of 5 is an All-Star season.

It looks like the rate was pretty high for most of 1955-67. Six of those seasons were at least 0.4 and that mark has been eclipsed in only 2 seasons since then. There has been an upward trend since 2004.