Ten-Fold Stars

30 Win Shares in a season is a level achieved only by the top stars of the year -- at 30 Win Shares a player is often getting into MVP territory (in the NL last seaosn only David Wright, Albert Pujols, Miguel Cabrera and Matt Holliday had 30 or more Win Shares). To total 300 or more Win Shares in a decade means essentially a player has averaged MVP-type level play year after year over the entire decade. As you might expect, then, this feat has been rarely accomplished. Over the past five complete decades (1950s through 1990s), only six players have topped 300 Win Shares over a full decade:

1950s: Mantle, 317 Win Shares
1960s: Aaron 340, Mays 337, Frank Robinson 307
1970s: Joe Morgan 315
1980s: none
1990s: Bonds 351

In the current decade that will run from 2000 to 2009, with two seasons remaining three players have enough Win Shares accumulated to make 300 plausible:
--Barry Bonds has 277 over the period 2000-2007, and if he does latch on with a team he could still make it to 300 over 2000-2009.
--Alex Rodriguez has 271 over 2000-2007, and based on recent performance will likely make it easily to 300 over 2000-2009.
--Albert Pujols has 251 Win Shares, and again based on recent performance he should make it to 300 by 2009, though any substantial dropoff in performance, as unlikely as that is, or significant injury would leave him short. Albert is a bit behind Bonds and A-Rod in this decade only because Albert only first broke into the majors in 2001, so he has one year, 2000, with zero Win Shares.

For those interested in earlier history, the 300+ Win Shares decades for the first half of the 20th century were:
1900s: Honus Wagner 421 Win Shares
1910s: Cobb 386, Walter Johnson 378, Tris Speaker 361, Eddie Collins 338
1920s: Ruth 413, Hornsby 362
1930s Ott 323, Gehrig 323,Foxx 314
1940s: none