SHANGHAI — If you’re a “single dog,” a “bare branch,” a “leftover man” or a “leftover woman” — all monikers for unmarried Chinese — you may find Valentine’s Day particularly trying.

Judging by the numbers, quite a few of the long faces on Tuesday should belong to men.

That’s because China’s gender gap remains huge. There were 33.59 million more men than women in China in 2016, according to figures from the country’s National Bureau of Statistics that were issued last month, and 48.78 percent of China’s 1.38 billion people are female, compared with a global average of 49.55 percent.

For men, especially those lower on the socioeconomic ladder, marriage can be hard to attain.

The reasons for the gap are well known: a traditional preference for boys, compounded by the “one child” policy instituted in 1979 that led millions of couples to abort female fetuses. Worried by one of the world’s lowest fertility rates, the government changed the policy last year to permit all couples to have two children.

On Valentine’s Day, “I see a lot of stressed-out people around for different reasons,” said Li Xuan, a psychology professor at N.Y.U. Shanghai who studies fatherhood and relationships.