It's true what they say: Absence really does make the heart grow fonder.

That's one key takeaway from a new Pew Research Center poll on Europeans' attitudes toward the European Union. Since Brexit, the attitude toward the institution has improved in many countries, including the U.K. In Poland, for example, nearly three-quarters of the population say that they have a favorable opinion of the European Union. It's about as high in Germany and Spain. About half of all Britons say they support the E.U., up from 40 percent a year ago.

A couple other key findings: The European project is most popular among Europe's youngest residents. A whopping 73 percent of those surveyed between the ages of 18 and 29 support the organization. Just 58 percent of Europeans 50 and older feel the same way. People on the left are more likely to like the E.U. than those who call themselves conservative. Also of note: A majority of those surveyed say Brexit will be bad for the U.K. And a majority of Britons say their leaving will be bad for the “European project.” They're more divided on what that means for the U.K.

Unsurprisingly, Greeks (who've suffered under austerity measures) have the worst opinion of the governing body. Just a third of the country views the E.U. favorably.

Support for the E.U. coincides with renewed economic confidence across the continent. The euro zone economy grew significantly in 2016, a trend that's continued. Unemployment has dropped to the single digits, and job creation accelerated to a nine-year record at the beginning of this year.

It's not all good news for Brussels, though. As the report's authors explain, “while few citizens on the European continent are eager to see their own country depart the E.U., many want the chance to have their voice heard through their own referendum on E.U. membership.” That's due, largely, to frustrations about the refugee issue and the E.U.'s economic management. More than half of all Europeans also want their countries to be able to make their own trade deals with other countries. And nearly three-fourths want their countries to control future migration from outside the E.U.

Immigration is a particularly thorny issue for the European Union. Millions of people have come from Syria and North Africa to Europe during the past two years, many making their way by boat or over dangerous land crossings. In 2015, at least a million migrants made their way to Europe, a huge jump from 2014. That's led to increased concern about crime, terrorism and displacement.

Now, many Europeans want their home countries to have more of a say about who can come — and who can stay. More than 80 percent of all Hungarians say their government should make their own decisions about who can and can't immigrate to their country. About 77 percent of Poles; 75 percent of the French and three quarters of all Germans agree. The numbers are nearly as high in Italy, Spain and Greece.

Majorities in the countries surveyed also want their governments to have more control over one of the founding freedoms of the E.U. — the free movement of people. In 2015, about 1.4 million people migrated from one E.U. state to another. In the Pew survey, most people said they wanted their governments to be able to set their own limits.

But giving countries more autonomy on immigration and trade would run counter to the European Union's core mission. “If they back away from the principle itself, that's a very severe blow to the bedrock assumptions of what the E.U. is for,” said Joshua Cole, a professor at the University of Michigan in Ann Arbor. “It means the European project as it was originally conceived is really being rethought.”

Negotiating trade deals separately would also, he said, run counter to the project's central raison d'être. “The European Union is about Europe acting as a union. That's what it means. You can't really suggest that it would be better moving forward for countries to negotiate their own deals,” he said. “If that's the case, the European Union is redundant.”

The Pew survey also found widespread antipathy toward political parties in the respondents' own countries. As the report's authors write:

Few political parties in Europe enjoy widespread appeal. The few that buck this trend tend to be more established parties in Western European nations that have not suffered as much economically in the years since the euro crisis. Sympathy for the frequently Euroskeptic parties to the right of the political spectrum is limited: In no country surveyed does more than about a quarter of the adult population hold a favorable view of parties such as France’s National Front, the Netherlands’ Party for Freedom (PVV) or Britain’s UK Independence Party (UKIP).

A note on methodology: Over about six weeks in March and April, 9,935 people were surveyed in France, Germany, Greece, Hungary, Italy, the Netherlands, Poland, Spain, Sweden and the United Kingdom.