Supporters of Catalan independence wave separatist flags during a demonstration organized by the University of Barcelona in Barcelona on Sept. 28. (Geraldine Hope Ghelli/Bloomberg News)

After a chaotic and at times violent referendum Sunday, the Catalan government announced that 90 percent of ballots cast had favored independence from Spain — even though the Spanish government in Madrid declared the vote illegal. But what comes next?

For Catalans hoping for independence, some clues could possibly be found in South Sudan. These clues may not necessarily be reassuring, however.

That's because, although there are plenty of independence movements around the world — the same week as the vote in Catalonia, Iraqi Kurds held their own referendum on breaking away from Baghdad — not many such movements have been successful in recent years.

In fact, over the past quarter-century, only nine new countries have been created, adding to a total that now stands at nearly 200 worldwide. And the experiences of these countries produce some mixed lessons for others hoping to follow their path. Here's the list:

  • South Sudan
    South Sudan declared independence from Sudan on July 9, 2011, after a violent war with the ethnically Arab north that lasted decades. Almost 99 percent of voters supported independence in a referendum, and the new country was swiftly recognized by the international community. The United States played a key role in South Sudan's journey to statehood.
  • Kosovo
    Kosovo declared independence from Serbia on Feb. 17, 2008. The country had been administered by the United Nations since 1999, when NATO bombed Serbia and forced then-President Slobodan Milosevic to withdraw his troops from the ethnically divided province.
  • Montenegro and Serbia
    The single nation of Serbia and Montenegro, formed after the collapse of Yugoslavia in 1991, changed into the State Union of Serbia and Montenegro in 2003, and finally into the two separate states of Serbia and Montenegro in 2006.
    It was Montenegro that ultimately ended the relationship, with a referendum on May 21, 2006, when just over 55 percent voted to separate from Serbia. On June 3, Montenegro declared independence. A few days later, Serbia followed suit.
  • East Timor
    East Timor, now also known as Timor-Leste, achieved independence on May 20, 2002, but the country had effectively voted for independence years before, when a referendum delivered a vote that clearly rejected the proposed “special autonomy” within Indonesia. After that referendum, there was brutal violence in the region, with pro-Indonesian militias attacking Timorese, and a special U.N. force had to be deployed to the country.
  • Palau
    Palau, geographically part of the larger Micronesia island group in the western Pacific Ocean, is the least populated country on this list, with a little over 21,000 people living on about 250 islands. It became independent on Oct. 1, 1994, 15 years after it had decided against becoming part of Micronesia because of cultural and linguistic differences.
  • Eritrea
    The United Nations established Eritrea as an autonomous region within the Ethiopian federation in 1952. However, when Ethiopia, under Emperor Haile Selassie, annexed the region in 1962, it sparked a civil war that lasted 30 years. In 1991, the Eritrean People's Liberation Front (EPLF) ousted the Ethiopian forces, and on April 27, 1993, the country declared independence after a referendum.
  • The Czech Republic and Slovakia
    On Jan. 1, 1993, Czechoslovakia was separated by parliament into two countries: The Czech Republic and Slovakia. After the “Velvet Revolution” ended one-party Communist rule, it was the “Velvet Divorce.”
    Immediately after the split, there appeared to be some trepidation: The New York Times noted “wide regret” over the end of the nation that was formed after World War I. However, the contemporary view is that the split was a (relative) success: “The split was really smooth,” Slovakian journalist Pavol Mudry told the BBC in 2013.

So, what lessons can be learned? It's clear that there has been no easy path to independence in recent years. Of the nine nations above, four were formed as a direct result of civil war. Five were the result of the collapse of communism in Europe — a unique historical watershed and one that produced all sorts of upheaval. A number remain troubled states: Eritrea has been dubbed the “North Korea of Africa.”

Countries such as South Sudan and Kosovo had major international backers, notably the United States, in their bid for independence — something Catalonia does not have. Even then, their paths to independence have been rocky. Kosovo still lacks recognition from a number of states and has not applied for U.N. membership, while its economy remains underdeveloped. South Sudan is still beset by ethnic violence and famine.

Even clearly successful independence bids have their drawbacks. Montenegro has joined NATO and hopes to join the European Union, but a coup attempt occurred just last year, and there have been long-standing corruption allegations. More than two decades after independence, the Czech Republic officially created a new name, Czechia, after a bitter internal debate about its lack of international recognition. (The Washington Post's style is still to write the formal long name, the Czech Republic.)

But it isn't just Catalans who should study this recent history — Spanish leaders in Madrid should pay attention, too. In many of the above cases, it takes decades for the demand for independence to reach a tipping point. And as the still-lingering hopes of Scottish independence after a failed 2015 referendum have shown London, once the genie is out of the bottle, it is very difficult to put it back in.

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