今年のＭＶＰ、最優秀新人選手、ベストナインの投票について各ＮＰＢ選手のWin Shares（ウィン・シェア）を計算しました。Win Sharesの日本語の説明はこちです。

I’ve written in the past that I use Bill James’ Win Shares methodology to generate my short list of candidates for my postseason award votes, the MVP, Rookie of the Year, Best Nine and Gold Gloves. It’s not an easy system to use, but has two very attractive features.

1. The wins attributed to a team’s players cannot exceed the number of wins the team achieves.
2. Because it works from the concepts of league defensive norms at different positions rather than raw fielding numbers — that are often skewed toward poor teams that have allowed more base runners.

The system also has many inherent flaws particularly the lack of loss shares — something James is ostensibly still working on — to account for defensive responsibilities and playing time.  The proposed new system would give every player a win-loss record, where the current system has to make do with a single figure.

This comes into play when you compare, for example, two DeNA BayStars outfielders, Yoshitomo Tsutsugo and Neftali Soto. Win Shares assigns Tsutsugo, the Japan cleanup hitter, with 22.5 percent of the club’s offense win contribution, and Soto — who also hit 38 home runs but in just five months and who was vastly more productive with runners on base and in scoring position — with 21.3 percent.

But here’s the catch, Soto made 7.7 percent of the BayStars’ batting outs, while Tsutsugo made 9.4 percent, a 20 percent increase. If we were assign the two loss shares to go with their win shares, I’m guessing Tsutsugo would be 22-11, while Soto was 19-7 and probably more valuable.

This sometimes creates disconnects for a variety of reasons. Two players with identical production on teams playing in similar offensive contexts can have quite different win share totals. If one team wins more games than its totals of runs and runs allowed would suggest, that team will have more wins to divide up among its players than a team that got fewer wins than expected.

A surprise from this year’s win shares calculations involved Yakult Swallows closer Taichi Ishiyama. He finished second in pitching win shares in the Central League behind Tomoyuki Sugano. How could that be?

Because the Swallows’ parks this year gave them the highest run adjustment — meaning runs were easier to come by in their games than in any other team’s in Japan this year — Yakult’s 658 runs scored — the second-highest CL total was not nearly as impressive as their CL-worst 665 runs allowed. Win Shares estimates the Swallows scored 297 runs more than the worst offense imaginable would score, but saved 416 runs more than the worst possible pitching and defense would allow.

That gives a huge amount of the credit for their 75-win total to the pitching and defense, and since the Swallows also won more games than expected given the number of runs scored and allowed — it means pitchers who excelled for them this season could potentially be credited with contributing to more wins than expected.

According to Win Shares, the top 10 CL pitchers this season were, in order:

1. Tomoyuki Sugano,
2. Taichi Ishiyama
3. Katsuki Azuma
4. Daichi Osera
5. Yasuaki Yamasaki
6. Onelki Garcia
7. David Buchanan
8. Yasuhiro Ogawa
9. Randy Messenger
10. Kris Johnson

I would never argue that’s right, but there are bits of truth that the system can illuminate.