Even a casual look at NPB baseball records clearly shows that from the founding of NPB through 1944 was a pitcher dominated era. When I was trying to evaluate the major league capabilities of NPB stars who played in this time frame, I had to measure the size of this effect as best I could. I used the matched at bats method I've used several times in the past, and came up with 155 players who batted at least once before 1945 and at least once after 1945. They had a total of 61,461 matched at bats. The comparison is as follows:

Initially, all I did was the research on the hitter data set out above. Since then, I've learned that if you want to evaluate pitchers, you've got to do it from matched innings by pitchers if possible. So I found the 41 pitchers who had at least 1/3 IP before 1945 and at least 1/3 IP after 1945, and checked their matched innings before and after 1945. I came up with 15,457.2 matched innings with the following results:

	IP	H	HR	BB	K
Before	15,457.2	10,736	204	6910	6409
After	15,457.2	14,942	799	4840	4966

There are two factors we haven't addressed: parks and players ages. While I haven't investigated it, I'd expect that each set of parks was about neutral for its own time frame. However, the players in the "after" group are always older by a few years than their matched at bats from "before". It is clear that aging alone cannot come close to accounting for differences of this magnitude. It would be nice to try and filter out the effect of aging, but I have yet to see any study of aging which would enable us to do so. That said, we must realize that aging has some effect on the data in the studies.

One can derive conversion factors from these two sets of data (I'm using post 1945 as the base), and I will do so for both the hitting and pitching data in categories common to each set of data:

Interestingly, even though there was expansion in the number of teams after 1945, the effects are more pronounced for the pitchers. Maybe the pitchers had already paid a heavy price for the training methods and pitcher usage patterns of Japanese ball at the time, but I suspect it would have to be both to be a reasonable explanation in and of itself as many of the pitchers studied had limited pre-1945 use. In any event, both sets of data show hits up sharply, though nowhere near as sharply as homers, which shot through the roof. Walks and strikeouts are both down a large amount.

I'd like to know more about pre-1945 ballparks, but I'd suspect the post-1945 ballparks did a much better job of making the home run a part of the game. Balls may have been bouncier because rubber was no longer being reserved for military use. Also, many young men who had been in the service (or would have been had the war continued) were now available to play ball.

For a while, I puzzled over the way walks and strikeouts dropped in tandem given the rise in hits and power hitting. My initial reaction was that hitters would have been swinging more freely, which I would expect would eliminate the likelihood of a drop in the strikeout rate. I was a little surprised pitchers didn't walk more guys, as I thought they might well mimic the reaction of the majors in the 1920's and work more carefully to hitters, thus raising walk rates. It seems like the Japanese either by plan or accident realized the truth that if you walked someone and he was batted in via an extra base hit, he scored. That means it's even more important to limit how many free passes you issue when power is a greater part of the game. One conclusion I make from this data is that before 1945, Japanese hitters more consistently worked pitchers deep into counts in hopes of drawing a walk, but at the price of striking out more often. When hitting and power rose so sharply after 1945, there was a lesser emphasis on just waiting for a walk and more on trying to get a hit, it would seem.

Just looking at the hitters' data, the same hitters with the same number of at bats had 14% more hits after 1945, with a little over one-half of the increase in hits coming in the various extra base categories. On base percentage rose only about 2%, however, because after 1945 walk totals down so much. Slugging percentage rose 21%, largely due to the rise in extra base hits.

I'll leave further interpretation of the data to others at least for the time being. However, the data seemed far too important to fail to report it.