"Not surprisingly, the most active bloggers are younger people who have grown up during the blogging "revolution", which started about seven years ago. Bloggers in the 21-to-35 year-old demographic group account for 53.3% of the total blogging population. This group is followed by the generation just behind them - people 20-years-old or under are 20.2% of the blogging landscape. This group is closely followed by 36-to-50 year-olds (19.4%), while bloggers who are 51-years-old and older only account for 7.1%.
The difference between genders in the blogosphere is balanced with women making up 50.9% and males 49.1% of bloggers. This suggests the Internet is a gender neutral environment."
Source: Inside Blog Demographics, Sysomos, June 2010