So what's with all the no-hitters? Hey, folks, that's baseball

Jaded yet? Since Ubaldo Jimenez fired the season's first no-hitter on April 17, three other pitchers have climbed that same mountain. On Friday night in St. Petersburg, Edwin Jackson joined Jimenez and perfectionists Roy Halladay and Dallas Braden in holding the opposition hitless With a bit more than half the season to play, 2010 stands with nine others in a tie for 11th place, having produced four no-hitters.

With four no-hitters in such a short period of time, there's a natural tendency to look for reasons why such a cluster would come about. This isn't actually that unusual, even in modern baseball history. Back in 1990 there were four no-hitters in June alone, capped by Dave Stewart and Fernando Valenzuela each tossing one on June 29. A year later, there were five no-hitters in a two-month stretch starting just before the All-Star break, including two combined no-hitters and a perfect game by Dennis Martinez. Those two seasons, '90 and '91, are tied for second place all-time in number of no-hitters thrown at seven, and they hold the modern record. (There were eight no-hitters in 1884, a year in which the presence of a third major league diluted talent and made extreme performances more possible.) Looking just at seasons since 1901, when the stable two-league structure came into being, we can see that 2010 is already among the top seasons for no-hitters (all 2010 stats are through Sunday's games):

That last column is important, as what we're really interested in isn't the raw number of no-hitters, but their frequency. Constant expansion and the lengthening of schedules mean that there are twice as many MLB games in 2010 as there were 50 years ago. You have to consider that in determining how common no-hitters really are. Once again, cutting things off at 1901 -- six of the top eight seasons are from the 19th century, as rule changes and the constant shuffling of leagues produced performance extremes -- here are the top 10 seasons for no-hitter frequency:

So far, 2010 stands out in this crowd, but we're talking about almost a half-season of games, which is just one reason to take what we've seen with a grain of salt. As you can see, no-hitters do cluster a little bit in lower-offense eras, such as the pre-World War-II period, the 1960s, and the offensive trough that preceded the modern era of hitting, stretching from 1988 through 1992. There were few no-hitters in the late 1920s and early 1930, when batting averages were at all-time highs.

No-hitter frequency should be affected by context, and the three factors that will have the largest effect are strikeout rate, home-run rate and league defensive range, as measured roughly by batting average on balls in play. Strikeout rates in MLB are at an all-time high, the product of the growing acceptance of the whiff as a byproduct of walks and power, which has diminished the stigma of walking back to the dugout bat in hand. The league home-run rate is its lowest since 1993, and the league BABIP is .298, lowest since 2005. All things considered, it should be easier to throw a no-hitter in 2010 than it has been in close to 20 years.

"Easier," however, doesn't mean "easy." No-hitters are incredibly rare events, happening about once every 1,400 regular-season games since 1876. They happen from zero to eight times a season, and while they can be helped along by the overall offensive context of the league, they can't be made by them. There were 14 no-nos in 1990 and 1991, but just two in the other two low-offense seasons that surrounded those years. During the second dead-ball era, from 1962 through '68, there were at least three no-hitters every year... except for 1966, when we saw just one.

The stretch of no-hitters over the last two months is a historical curiosity rather than a revolution. The infrequency of no-nos renders any clustering of them statistically insignificant, no matter how much we may scratch our heads. While the conditions of the game do make no-hitters slightly more achievable than they were in recent years, the best explanation for the last two months is a shrug, a wry smile, and the words, "That's baseball.'