I found some interesting data for the USA:
http://www.cdc.gov/nchs/data/nhsr/nhsr036.pdf
The data basically show this:
There are more males who are not getting laid than women not getting laid.
There are more males fucking 4+ people a year than there are females fucking 4+ people a year.
There are more famales fucking 1 or 2 people a year than there are males.
So women are more likely to be fucking consistently, and on average 1 or 2 people a year. Men are more likely to either not be fucking or be fucking a higher amount.
So the top players are effectively sharing a larger pool of women.
Here's the data for the 20-24 age range:
Women with X sexual partners in the past year...
0: 4.7%
1: 57.8%
2: 14.1%
3: 5.1%
4+: 4.6%
Men with X sexual partners in the past year...
0: 5.9%
1: 49.8%
2: 12.2%
3: 6.8%
4+: 9.5%
The thing is, this doesn't ask about NEW sexual partners in a year. Many of these people, male and female, are probably in some sort of LTR so their sexual partner for the past year is the one they've been with forever.
Either that or they're just only getting one-off sex once a year. So let's just discount people who only have 1 sexual partner a year and see who is a bit more active:
Women...
2: 14.1%
3: 5.1%
4+: 4.6%
Total = 23.8% of women aged 20-24 with more than 1 partner a year.
Men with X NEW sexual partners in the past year...
1: 12.2%
2: 6.8%
3: 9.5%
Total = 28.5% of men aged 20-24 with more than 1 partner a year.
So men are indeed on both extremes. More likely than women to be virgins, more likely than women to be not getting laid in a given year, but also, more likely to be getting more than 1 sexual partner a year.
So, roughly speaking, 28.5% of young single men are chasing after 23% of young single women.
Hence, sausagefests.