Post–World War II economic expansion brought a wave of immigrants to South Florida from the Northern United States, which significantly increased the population in Miami Beach within a few decades. After Fidel Castro's rise to power in 1959, a wave of Cuban refugees entered South Florida and dramatically changed the demographic make-up of the area. In 2017, one study named zip code 33109 (Fisher Island, a 216-acre island located just south of Miami Beach), as having the 4th most expensive home sales and the highest average annual income ($2.5 million) in 2015.