The growth of the regional population was particularly sustained during the 1950s–60s, thanks to a prolonged economic boom, high birth rates, and strong migration inflows (especially from Southern Italy). Since the 1980s, Lombardy has become the destination of a large number of international migrants, insomuch that today, more than a quarter of all foreign-born residents in Italy live in this region. , the Italian national institute of statistics (ISTAT) estimated that 1,139,430 foreign-born immigrants live in Lombardy, equal to 11.4% of the total population. The primary religion is Catholicism; significant religious minorities include Christian Waldenses, Protestants and Orthodox, as well as Jews, Sikh and Muslims.