by Clay Davenport

More serious a problem is the small number of players moving between Japan and the United States. The Translations system depends on being able to set a difficulty level for each league. To do that, I need to have a sizable group of players who have played in both the leagues I am testing and in leagues whose difficulty level I already know. Every player who played in both leagues needs to be compared to the league average; if, as a group, one set is league average, and the second set is 10% above average, you can assume that the second league is 10% worse that the first league.

With the Japanese leagues, there really haven't been enough comparisons to get a firm grip on the appropriate difficulty level, especially since almost all the comparisons were of players who went from the U.S. to Japan, and not from Japan to the U.S..

Last year, for the first time, there were more common plate appearances from the prior year moving from Japan to the U.S. than vice versa. (A common plate appearance is the lesser of a player's plate appearances in League 1 and in League 2; it is what I use to ensure that a given player is always weighted equally.) Alex Ramirez was the only player who went to Japan last year to log more than 100 CPA, while five players--Ichiro Suzuki, Tsuyoshi Shinjo, Orlando Merced, Tony Fernandez, and Lou Merloni--came to the U.S. and reached that standard.

Using one-year differences, here's how the difficulty ratings for Japan shape up:

You can do the same analysis with Triple-A players. In fact, it is better to use Triple-A players: the Japanese leagues have generally taken players who were stuck in the minors, guys who tend to end up in Triple-A again even if they come back. There have been far more common PA between Japan and Triple-A than there have been between Japan and the majors.

In Baseball Prospectus 2001, I wrote that the difficulty level of Japan was "about even with the Triple-A leagues." Looking at it more comprehensively--I was basing my assessment on a scattering of players, rather than off a full list of Japanese player data--that was a silly thing to say, as the Japanese leagues have clearly and consistently rated as tougher than the American Triple-A leagues. Every case from the 1990s shows that players do worse as a CPA-weighted-average group in Japan than they do in Triple-A, and by a considerable margin. The Triple-A/majors multiplier is .860; if the transitive property holds, then Japanese EqA is worth about .948 of a major-league EqA, which conveniently enough is almost identical to what we got from major leaguers.

You can, of course, do the same thing with pitchers. The total ERA ratios for those come out as:

Triple-A weighted average:       17991 IP     1.154
Major league weighted average     7178 IP      .903

Remember, though, this is in runs, and runs are proportional to EqA to the 2.5 power. These ratios, in EqA terms, are the same as 1.058 and .960. The 1.058 between Triple-A and Japan is equivalent to a .910 ratio between Japan and the majors. So we have, all in EqA and major-league terms:

Hitting Triple-A to Japan         .948
Hitting Major Leagues to Japan    .946
Pitching Triple-A to Japan        .910

Pitching Major Leagues to Japan   .960

The mean of these values is .941.

For perspective, the Federal League, compared to the AL and NL of the mid-teens, rated as .93 and .95 in its two years of existence. It is considered a major league. The American Association of the 1880s lasted nine years; compared to the NL of the same era, it rated as low as .78 (in its debut year), and eventually got as high as .94. The AA is considered a major league. The Union Association only existed for one year, 1884, and it rated at .71, about the same as the present Midwest League. It is considered, by Major League Baseball, to have been a major league (a very bad decision, in my opinion; the St. Louis team, led by Fred Dunlap, was major-league quality, but no other team in the league was.) The Players League of 1890 actually rated as stronger than the NL, with a 1.01 rating. The American League of 1901, when Nap Lajoie hit .426, has a rating of .93.

The Japanese leagues meet or beat all of them. By historical standards, the present-day Central and Pacific Leagues are fully deserving of the "major league" label.

Japanese Ballparks

We've all heard about the tiny little Japanese ballparks, and the impact they have on the home-run totals of visiting Americans. That isn't so true anymore. A wave of stadium building swept through Japan over the last 15 years; all six stadiums in the Pacific League, for instance, have been built or remodeled since 1988, although the Central league still has two parks from the 1920s. The remade stadiums are only slightly smaller than their American counterparts.

At least, that's true of the primary stadium for each team. Japanese teams apparently schedule a number of games away from their nominal home stadium. Of the 70 home games played by the champion Yakult Swallows in 2001, only 59 were played in their Jingu Stadium home. They played three games in Fukuoka (home of the Pacific League's Daiei Hawks; there is no interleague play in Japan, so it's like having the Yankees play in Shea Stadium), two in Chiba Marine Stadium (home of the Chiba Lotte Marines), two in Sapporo, two in Morioka, one in Nagano, and one in Sendai. I have no idea how large these outside stadiums are.

Of course, size isn't the only issue for how a park plays. From looking at their dimensions, I expected the two 1920s parks--Yakult's Jingu Stadium and Hanshin's Koshien Stadium--to be wildly divergent. Jingu has very small dimensions, while Koshien is a lot more spacious. Americans playing for Yakult have done better than expected; Americans playing for Hanshin have done worse. I fully expected Yakult to have a Coors-like park factor, and for Hanshin to look like the old Astrodome.

The game-by-game records for the last two years were available online, so I compiled park factors for Japan exactly the way I do for American teams. What I thought would show up didn't happen at all.

The parks:

The opinions I read indicate that everyone thinks the Tokyo Dome, where the Giants and Fighters play, is an extreme hitters' park; it may be that the Yomiuri score in 2000 was an aberration.

Later this week, we'll look at the top players in Japan over the last few seasons.

Clay Davenport is an author of Baseball Prospectus. You can contact him by clicking here.

Clay Davenport is an author of Baseball Prospectus. You can contact Clay by clicking here or click here to see Clay's other articles.

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