If getting rich is hard for individuals, it is harder still for nations. Of more than 190 countries tracked by the International Monetary Fund, fewer than 40 count as wealthy or advanced economies. The rest are known as emerging nations, and many of them have been emerging forever. The last large country to make it into the advanced class was South Korea, 20 years ago. The next major nation likely to join that club could be Poland, an under-the-radar economic star that President Trump will visit this week on his second overseas trip in office.

Mr. Trump will meet with leaders of the ruling Law and Justice party, who are thrilled that he has chosen to visit Warsaw before Berlin, Paris or Brussels, and participate in a meeting to promote regional economic ties in Eastern Europe. Other European leaders are unnerved by how Mr. Trump’s populism echoes the right-wing nationalism of his Polish hosts — both have been attacked as illiberal threats to the postwar Western order. But so far, two years of populism has not derailed a quarter-century of steady economic progress in Poland.

The I.M.F. has a complex definition of “advanced,” but a common thread is that all the nations have a per-capita income of at least around $15,000. Since Poland completed the transition from Communism to democracy in 1991, its economy has been growing at an average annual rate of 4 percent and, remarkably, has not suffered a single year of negative growth. In those 25 years, Poland’s average income has risen to near $13,000, from $2,300, and it is now on pace to pass the $15,000 mark by the turn of this decade.

This is testimony to the long-term fiscal sobriety of Poland’s leaders, and its sharp break with Communism. After the collapse of the Soviet bloc, Poland set out to distance itself as far as possible from Russia, and adopted the financial discipline and institutional reforms required to join the European Union.