You may have heard that starting this season, all teams in major league baseball will be storing balls in humidors. If you haven't heard about it, don't feel bad, I almost missed it myself. In fact, I only learned late last year that the Colorado Rockies had been using them since 2002.

What is a humidor? It is a room in which both the temperature and the humidity level are kept constant.

Why store the balls in humidors? As you surely know, the Rockies' Coors Field has the highest rate of home runs hit in the majors. It also happens to be the highest stadium in the majors. This fact, and this fact alone, has been consistently blamed for the high production rate.

However, the Rockies started to think outside the box. Denver is a very dry place. As things like baseballs dry up, they become harder. A harder baseball will travel farther when hit. To combat the effects of dryness, they put the balls in a humidor.

The effect was that every year since, the production rate has been dropping to levels more in line with the rest of the league. It wasn't the altitude after all, at least, not all by itself. This pleased pitchers as now they were not as shell-shocked as in the past.

It might have been left at that if not for some controversy last year. It was argued by some that the humidors gave an unfair advantage to the Rockies. Never mind that this is ridiculous because both teams play with the same balls. Besides, have you seen how the Rockies have been playing lately? On the other hand, they did have a much better home record last season.

Still, MLB decided that every team should do the same. Every one must be uniform so every team must now use the humidors.

Actually, this is not quite correct as far as I understand it. Every team must now store the balls in a temperature-controlled environment. It does not have to be a humidor. The distinction is important.

I have seen very little about how this will affect production throughout the league. I have seen a few player ratings mention the humidor in that it will affect a certain player's stats in one way or another. They call this the humidor effect. Rotowire has a small article mentioning the fact in general and they suggest, in the last line, that production will actually go down dramatically. They base this prediction on the fact that it reduced production at Coors Field.

I take a more scientific approach.

First, I gathered humidity data for all major league cities. I then found out the specifications of the humidors. MLB says to store the balls in controlled environments of 70 degrees and 50 percent humidity. The balls must be stored there as soon as they are received and not to be taken out more than 20 minutes before the start of the game. This information is very important in my study.

The average humidity level in all major league cities is 57 percent. Taking away Denver at 40 and Phoenix at 23, that average goes up to 59 percent. Keep in mind these are yearly afternoon averages. It is usually more humid in the morning and less in the evening when most games are played. Also, a handfull of cities are more humid between June and September, the two months for which I have data.

So the balls will have, on average, a humidity level lower than the actual humidity where it will be used. As Colorado showed, a harder ball will travel farther. We can therefore expect a higher home run rate in the more humid cities like Los Angeles, San Diego, Milwaukee and Miami.

But levels change during the year. Seattle is humid at 62 percent (third behind Los Angeles and Milwaukee) if we take the yearly average but is only 53 in June. Remember that the balls will be at 50 percent. That means that early in the year, the Mariners can expect a normal home run rate which will remain constant throughout the season even when it hits 83 percent in September.

How will the humidity level affect the balls once they are taken out to be used?

It seems to me that the balls will absord the ambient humidity and become less hard. This means that home run rates should be higher at the start of games in the hot days of summer and come back to normal in the later innings.

I'm no scientist and I don't know how fast a ball will absorb the ambient humidity. A couple hours may not be enough to make a big difference. I also don't know how a ball with 50 percent humidity will react being suddenly put in a 70 percent humidity environment. The two factors may have the reverse effect and rates may go down.

Looking at my humidity chart, not many cities have average humidity levels in June. Most are actually fairly close to that 50 percent level at that time of year and I assume in April as well. But if a baseball is stored at room humidity, it would presumably absorb the high morning humidity.

The question is therefore how fast does it lose that humidity. I'm guessing it would take a day or two. This means that with the humidors, the balls will be more standardized. They will be dryer than in the past meaning they will be harder and therefore, more home runs will be hit in general and probably more consistently through the season.

Things should remain virturally the same in Denver. As for Phoenix, dryer than 50 percent all year round, morning, noon and night, home run rates will go down. Depending on how fast the balls lose their humidity, home run rates will be higher in the second half of games.

So in general, I think that production will go up. The one remaining question is by how much is it going to be affected? In Denver, it dropped by just over 25 percent which just so happens to be the percentage difference between a humidity of 40 and one of 50.

I don't think it will be that dramatic. There are too many factors which we know nothing about as nobody ever studied them. We could however see as much as ten percent or more increase in production. That is my bold prediction.

The wild card is the fact that while all teams are directed to store balls in temperature-controlled rooms, these are not humidors. Again I'm no scientist but to me, temperature control is not humidity control. What will be the humidity level inside? If not at 50 percent then the whole theory goes out the window.

Also, apparently most teams were already storing balls in environmentally controlled rooms. We don't know which teams have been doing this. We also don't know which teams will have the full humidors this season. If most teams were already doing this, then there will be little change in 2007.

After the season, we can compare the numbers with the minor leagues. Since the minors will not be using humidors (as far as I know), they will become the control group. If the majors has a ten percent home run rate increase while the minors remain the same, we would have our answer. I must caution however that a few years pass before coming to that conclusion.

I believe that MLB is betting on production going up and may be in fact why they decided to do this. According to conventional wisdom, more runs and home runs means more fans. If you can find a way to somehow increase production artificially, throughout baseball, not just one city by taking the fences in for example, you put more fans in the seats. If not all teams will have fully functioning humidors this year, you can bet they all will very soon.