Anticipated demand in the United Kingdom
In the United Kingdom, the government is reported to have anticipated demand for same-sex civil partnerships as being around 11,000 to 22,000 by 2010. However, this appears to have been an underestimate; as of December 2006 some 15,657 such partnerships had been registered in around 9 months.

Source: http://en.wikipedia.org/wiki/Same_sex_marriage

I would say this is more than just an underestimate but a shows a lack of knowledge by those who compile these kind of reports and statistics.

These are the same people who tell the government the current trends, highs and lows in gay and lesbian lifestyles. They warn the government when "those" people are getting feisty.

They are quite obviously misinformed! So how do we correct it?