Joe Patronite/Getty Images

Joe Patronite/Getty Images

In 1988, the last time South Korea hosted the Olympics, North and South Korea were more alike than different, separated by an arbitrary line yet joined by history, language and the bonds of family.

Both Koreas had come a long way, emerging from colonial rule and rebuilding their economies after a devastating civil war.

But the Olympics in Seoul in 1988 ended up being a turning point. Over the past 30 years, the two countries have diverged sharply — economically, politically and culturally.

South Korea rapidly industrialized, growing at one of the fastest rates in the world. The North stagnated.

$30k $20k South Korea $10k North Korea GDP per capita $0 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 $30k $20k South Korea $10k North Korea GDP per capita $0 1820 1880 1940 2000 $30k $20k South Korea $10k North Korea GDP per capita $0 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 $30k $20k South Korea $10k North Korea GDP per capita $0 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 $30k $20k South Korea $10k North Korea GDP per capita $0 1820 1880 1940 2000 Source: Maddison Project Database . Data is estimated on the economies of the regions that would become North and South Korea. The Korean Peninsula was formally divided in 1945.

The South shed its military dictatorship and opened up to the world. The North remained isolated and authoritarian, and endured a devastating famine that killed an estimated 2 million people, according to some estimates.

Life expectancy 80 years South Korea 70 North Korea 60 North Korean famine 50 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 80 years South Korea 70 North Korea 60 North Korean famine 50 1960 1970 1980 1990 2000 2010 80 years South Korea 70 North Korea 60 North Korean famine 50 1960 1970 1980 1990 2000 2010 80 years South Korea 70 North Korea 60 North Korean famine 50 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 Source: The World Bank

South Korea now exports Samsung phones, Hyundai cars and popular soap operas. North Korea, hamstrung by sanctions, still relies on exports of coal, clothing and shellfish.

Top North Korean exports Top South Korean exports 1) Coal 1) Integrated circuits 2) Men’s outerwear 2) Cars 3) Women’s outerwear 3) Refined petroleum 4) T-shirts 4) Ships and boats 5) Mollusks 5) Vehicle parts Source: The Observatory of Economic Complexity , 2015

In 1988, North Korea did not even participate in the Seoul Olympics, and it mounted a deadly terrorist attack 10 months before the Olympics. On Friday, its delegation will march under a single flag with the South Korean team at the opening ceremonies of the Winter Olympics in Pyeongchang.

The display of athletic unity, however, belies the vast gap that has opened between the two countries in the three decades since the Seoul games.

Other Communist countries in Asia, including China and Vietnam, saw the collapse of the Soviet Union in 1991 as a warning, and they quickly reformed their economies and opened their markets. The North remained closed.

It pursued the development of nuclear weapons and long-range missiles, making it an international pariah. Although North Korea’s economy started to grow moderately in recent years, devastating sanctions imposed by the United Nations prohibit it from selling its leading exports, and the economy could be shrinking again.

When the Soviet Union collapsed, the North’s economy soon followed. Floods and drought compounded the situation, leading to a devastating famine. Food in the North is still rationed, with the best goods distributed only to a small group of elites with government connections.

By the time of North Korea’s famine, South Korea had become a booming cultural capital, exporting K-pop, its answer to American boy bands, to its former adversaries, China and Japan.

Pyongyang, 1996 South Korea, 1996 Associated Press; MBC via YouTube

South Korea became Asia’s leading exporter of culture — producing music, movies and television dramas.

At one time, both countries could afford to build intricate subways beneath their capitals. But a decade after the Seoul Olympics, only one government could afford to keep its trains running regularly.

Pristine and ornate as a national museum, the Pyongyang subway system is little used. Seoul’s subway stations are capitalist showcases plastered with movie posters and makeup ads.

Pyongyang, 2005 Seoul, 2006 Patrick Aventurier/Getty Images; Chung Sung-Jun/Getty Images

Built to showcase North Korean industry and double as atomic bomb shelters, the stations of the Pyongyang metro are decorated with revolutionary propaganda. The train cars, which have not been upgraded in decades, remain mostly empty.

Virtually all of North Korea’s early success – including its subway system – as well as its later misfortunes can be attributed to the country’s ruling family, the Kims.

The same family that ruled North Korea in 1988 rules it today. And the same authoritarianism pioneered by the country’s founder, Kim Il-sung, is continued by his grandson, Kim Jong-un.

In the North, all public gatherings are organized by the state. In the South, people are free to protest against the government.

Pyongyang, 2009 Seoul, 2009 Korean Central News Agency; Jeon Heon-Kyun/European Pressphoto Agency

At the time of the Seoul Games, South Korea had recently emerged from military dictatorship. Just eight years earlier, South Korean military forces massacred students and citizens protesting authoritarian rule.

When huge student and labor protests rocked South Korea again in 1987, the government deployed riot police officers and tear gas before eventually agreeing to democratic reforms.

Just over a year ago, protesters held candlelight vigils vigils every weekend for months to demand the impeachment of the country’s president, Park Geun-hye. The protests, which eventually led to Ms. Park’s removal from office, were uniformly peaceful.

Central to the politics of each country in recent years has been the North’s steadfast pursuit of nuclear weapons, which has led to sanctions and isolation.

Kim Jong-un, the North’s leader, is a veritable recluse who has alienated much of the international community. South Korea’s president, Moon Jae-in, has pledged to strengthen international alliances.

Kim Jong-un, 2017 Moon Jae-in with international leaders, 2017 KRT, via Associated Press; Pool photo by Jorge Silva

With the North participating in this month’s Games, will the two Koreas now begin to converge — or is it too late?

Just a few weeks ago, the idea of the North participating in Games would have been unthinkable. Mr. Kim spent much of 2017 developing and testing bombs and ballistic missiles in defiance of international demands.

Now, President Moon Jae-in of South Korea says he hopes the Pyeongchang Olympics could end a stalemate and propel the countries to talks.

In a sign of the easing tensions, the countries will not only march together during the opening ceremonies but will also compete as a single unified team in women’s ice hockey.

Ultimately, two countries that appear so different, even from space — where the lights of the South far outshine those of the North — have a shared history much longer than the three decades between Olympics. These Games may be a chapter in that history, but they are far from the last one.