The level of social construction did not significantly rise until minister Pierre Courant launched an ambitious plan in 1956, warranted by the increased rate of immigration from France's former colonies. Courant's plan had the goal of construction of at least 240,000 residences each year, and it was an unexpected success: from 1956 on, there were more than 300,000 new residences built annually, with a good number of them HLM. In 1964, there were 95,000 new HLM apartments. The residences were often constructed in large complexes, by "" ("the way of the crane"). The new, large apartment buildings were perfectly rectangular, to allow a crane to roll along a track and place components on both sides of the building simultaneously, saving both time and effort.