In the Cuban neighborhood of Little Havana in Miami, a man watches President Obama speak on Wednesday on a television in the Cuba Tobacco Cigar Company. (Charles Ommanney/The Washington Post)

President Obama’s announcement Wednesday of executive action on U.S.-Cuba policy was huge. By reestablishing diplomatic relations, expanding travel and trade, and encouraging investment, it reverses decades of policy. The president’s proposed measures do not end the embargo, which is a congressional prerogative, but they are wide ranging. What explains the timing of such a momentous shift? Political demography can offer a very useful analytical lens.

Obama mentioned demography in his speech, noting the Cold War context of 1961, the year he was born. The embargo, in fact, began the year before that. That policy was forged by a past generation and younger generations don’t support it. Gallup polls show that a majority of Americans have supported reestablishing diplomatic relations for 40 years, and about half have supported ending the embargo for the past 15. Cuban Americans, particularly in Florida, constituted the roadblock.

These days, however, Cuban Americans are young and ready to engage with the country of their parents or grandparents. In 2008, presidential candidate Barack Obama went to Miami and spoke about relaxing relations. The Miami audience, once the hardcore of the anti-Castro movement, was receptive. Democratic strategists are already emphasizing this point. Florida International University’s 2014 Cuba Poll shows, for example, that 88 percent of Cuban Americans age 18 to 29 supported reestablishing diplomatic relations, compared to only 41 percent age 65 and older. Cuban migrants who arrived in the United States more recently support that policy much more.

According to data from the U.S. Census Bureau’s American Community Survey (available from the University of Minnesota Population Center), there are 1.8 million Cuban Americans living in the United States, of whom 68 percent live in Florida (California, New Jersey and New York are the other popular spots). Slightly more than one million of those Cuban Americans are potential voters (U.S. citizens age 18 or older), less than 1 percent of the U.S. population. About 66 percent of them live in Florida, accounting for 5 percent of the state’s potential electorate – not a large percentage, but enough voters to make a difference in a traditional swing state.

Furthermore, 57 percent of Cuban Americans were born in Cuba. Within this group, 3 percent arrived before the rise of Fidel Castro (e.g., the grandparents of Marco Rubio, the Republican senator from Florida), 12 percent came in the years of the revolution (1959-64), 19 percent came in the Freedom Flight phase (1965-74), 16 percent came during the Marielito phase (1975-1989), and 50 percent arrived after the fall of the Berlin Wall and the tightening of the embargo (1990 to present). Each successive wave of immigrants is progressively younger – with median ages ranging from 76 among those who arrived prior to the revolution, 65 among those who fled the revolution, 60 among those from the Freedom Flight era, 56 among the Marielito generation, and 41 among those arriving since 1990. Overall, the average age of Cuban Americans is 40 years, slightly younger than the non-Hispanic white population in the United States (median age of 42), but there is a big generational gap between those born in Cuba (median age of 51) and those not born in Cuba (median age 21). This will almost certainly drive attitudes toward U.S.-Cuba relations in the future.

Demography also matters for understanding the timing of such a move from the Cuban perspective. For example, Cuban leadership will soon get younger. The Castros are octogenarians and President Raúl Castro announced in 2013 that he would step down when his term ends in 2018. Meanwhile, Cuba faces potentially serious consequences as its patron Venezuela faces a severe economic crisis. The Castros therefore needed a plan to hand power off to a new generation.

Further, Cuban demographics more broadly present a challenge. In 1960, the fertility rate of 4.7 was the highest that the island had seen since the end of World War II. It quickly dropped, however, facilitated by eased restrictions on abortion and increasing availability of contraceptives, aided by the increasing education and labor force participation of women. Fertility dropped to below replacement level around 1980. The result has been a type of demographic dividend for Cuba that has allowed it to survive economically – a fairly large fraction of the population in the labor force ages, with a small number of dependent children and older people. But with a rising life expectancy, the proportion of the older population is rapidly increasing. The demographic dividend is quickly coming to an end, to be replaced by a demographic disaster of a quickly aging population, with which it will be very expensive for an increasingly smaller younger population to cope. This may all happen after the Castro brothers die, but they can see it coming, and the island’s economy is going to be in even more desperate straits very soon. This is likely one reason why they are very open to overtures from the United States. Without handouts from Venezuela, they don’t have any other choice except to hope for an infusion of investment from the United States. Tearing down this wall could be the most effective long-term strategy for bringing a better life to Cubans.

Demography is often said to be destiny. There are of course many factors at play in U.S.-Cuba relations, but for both countries demography created incentives for historic negotiations.

Gregory Weeks is professor and chair of the political science and public administration department at the University of North Carolina at Charlotte. John Weeks is distinguished professor emeritus of geography and director of the International Population Center at San Diego State University.