 The study's authors conducted a series of studies using large amounts of census data (844,476 individuals) and conclude that immigrants who arrived from 1987–2004 paid only 57% of the taxes paid by average Canadian in 2006, with the effect that taxes from immigrants do not exceed the government expenses relating to them (a gap of $23 billion annually according to their numbers).A study by the C. D. Howe Institute suggests that immigration cannot keep Canada's population young and could possibly contribute to population ageing in the near term.Employment statistics have also brought into question whether skilled worker immigrants, with a 34% unemployment rate in 2001, are successfully meeting existing labour market needs in Canada.