Source? No really. This is shocking to me. 3% of Canadians work in construction and I suspect the majority of them are not working on housing. Do you mean 7% of the workforce participates in housing development and maintenance tangentially? Like, including lawyers, lobbyists, politicians, the portion of construction workers who aren't building roads and film sets, other craftsmen, people doing renovations, plumbers, hvac, insurance, inspection, etc.

Canada also has a lot of red tape around new builds that draws out the development process significantly, a lot of which necessitates all the other labor going into building too little housing for the population growth.