“Bulgaria has clearly benefited since it joined the European Union,” said Ruslan Stefanov, an analyst for the Center for the Study of Democracy, a Sofia-based think tank. “We’re richer, with a wider choice in terms of jobs and education across the bloc.”

The average Bulgarian now earns 440 euros, or about $470, a month, twice as much as when the country joined. Trade has increased significantly, as companies have taken advantage of membership in the bloc’s single market. Exports to European Union countries have doubled in the years since Bulgaria joined, and sales to other member states now account for two-thirds of all exports.

There have been other benefits. Tens of thousands of Bulgarians are studying elsewhere in the 28-member European Union — a greater proportion of its population than comparably sized member states like Austria, the Czech Republic or Hungary (this is partly a result, however, of the poor quality of Bulgaria’s education system).

Even more Bulgarians work and travel throughout the bloc, taking advantage of the region’s free movement of labor. That, according to Mr. Stefanov, has helped keep unemployment relatively low at around 8 percent — if Bulgarians cannot find jobs at home, he noted, they look abroad.

The European Union has also pumped in billions of euros in aid to help the country build new highways and roads, develop agriculture and rural areas, and protect the environment. Regular reports published by the European Commission on corruption and organized crime — persistent problems in Bulgaria — have kept local politicians on their toes (though Sofia has made little progress when it comes to uprooting graft and reforming its judiciary).

“The fact that Bulgaria is an E.U. member and there are a number of reforms on the way makes us believe that Bulgaria is definitely on the right track,” said Olivier Marquette, managing director for the Bulgarian operations of AES, a power company with its headquarters in Arlington, Va.