Surprisingly, the answer is that there are significantly more hard-throwing righties than lefties. Not just in total, but percentage-wise as well.
Baseball Info Solutions has been tracking the speed of pitchers for the last few years. Overall, about half of all pitchers (54% in the last two years) average 90 or more miles per hour on their fastball. It's nice to know that the rule-of-thumb we've been using is a good one. If a pitcher throws 90, he throws hard (in the top 50% of pitchers in baseball).
But amazingly, the hard-throwing lefty is not common. Over 70% of lefties are of the soft-toss variety. Only 37% of righties are soft-tossers.
Here are the details:
| Number of pitchers who throw 90 or more MPH when throwing a fastball |
| | Average Fastball 90+ MPH | Average Fastball Less Than 90 MPH |
| Right-Handed Pitchers | 270 (63%) | 160 (37%) |
| Left-Handed Pitchers | 47 (29%) | 114 (71%) |
| Total | 317 (54%) | 274 (46%) |
Note: Includes pitchers with 100+ fastballs thrown in 2005/2006.