It's been a long slow decline since the 1970s

Try 1960s. Diefenbaker abolished the racial requirement for citizenship in 1962. Pearson established the commission on bilingualism and biculturalism in 1963, which paved the way for official bilingualism and multiculturalism in 1971. He set up the point-based system for immigrant selection in 1967 to ensure the immigration process was nondiscriminatory. Trudeau began diversifying the immigration streams in the late 1960s.