Female gymnasts far out number male gymnasts.
In 2007 (most recent date I could get numbers for), there were 67,626 female gymnasts and 12,120 male gymnasts registered with USA Gymnastics, the national governing body for the US. That's already 5.6x more girls than guys.
But it gets worse as you look at the prime age range for male and female gymnasts. Look at the chart below* - in the prime years of elite competition for men (17 - 30) there are barely over 1000 athletes, while for women (15+) there are over 10,000.
Why are there far fewer male gymnasts? Two major reasons.
- Gymnastics is not a idealized sport for males.
Growing up, male gymnasts are accused of being effeminate or gay for prancing around in leotards. Unlike football, basketball, or baseball, it's rarely televised, and you don't earn a lot of social status for doing it, until everyone one day realizes that you are ripped (see: Gymnastics: Why is every male gymnast ripped?) I think this discourages a lot of guys from starting/continuing to pursue the sport.
- There are few places for male gymnasts to go after high school.
There is no NFL/NBA for gymnastics. There is college or an elite/national team. In 1980, there were one hundred and sixteen colleges with NCAA programs for men's gymnastics. In 2011, there were seventeen. This seven-fold decrease in twenty years has massively reduced the opportunities for male gymnasts to compete beyond high school. (In comparison in 2011, there were still eighty three women's teams) http://www.ncaapublications.com/productdownloads/PR2012.pdf
Much of this decline has been blamed (rightly or wrongly) on Title IX - a law passed in 1972 that was supposed to, among other things, encourage schools to create more women's sports programs, but instead caused schools to cut a lot of men's programs. Gymnastics was an easy target - lots of expensive equipment, not a lot of revenue. Very recently, the gymnastics community pledged millions of dollars to save UC Berkeley from losing it's program. You can learn more here about Title 9: http://usa-sports.org/TitleIX.pdf and UC Berkeley's challenges: http://newscenter.berkeley.edu/2011/05/02/gymnastics-to-continue-at-cal/
With a smaller pool of athletes, it's hard to have the depth necessary to field a great team every year, especially when you end up losing a few of the top folks every year due to injuries.
I want to point out that the US men's have fared quite well in recent years in face of this huge number disparity.
- We won Silver in 2004 as a team, with Paul Hamm earning Gold in the All-Around and Silver on the High bar. (US Women won Silver as a team + 1 gold, 3 silver, 1 bronze)
- We won Bronze in 2008 as a team, with Jonathan Horton earning Silver on the High Bar (US Women won Silver as a team, 2 Gold, 4 Silver, 1 Bronze)
- We won Prelims in 2012 as a team, but ultimately placed 5th in 2012. This indicates that we had the potential to win but failed to perform up to our capabilities in finals. Daniel Leyva also won Bronze in the all-around. (US Women won Gold as a team + 2 gold, 1 silver, 2 bronze)
* stats slightly skewed due to inclusion of Tumbling/Trampoline, Rhythmic Gymnastics, etc which are a small but non-zero portion of all gymnasts
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