I know I’m not alone. There are countless Americans who speak languages other than English outside their homes: not just those of us who have learned other languages in school or through living abroad, but also employers who have learned enough Spanish to speak to their employees; workers in hospitals, clinics, courts and retail stores who have picked up parts of another language to make their jobs easier; soldiers back from Iraq or Afghanistan with some competency in Arabic, Pashto or Dari; third-generation kids studying their heritage language in informal schools on weekends; spouses and partners picking up the language of a loved one’s family; enthusiasts learning languages with computer software like Rosetta Stone. None of the above are identified as bilingual by the Census Bureau’s question.

Every census in the United States since 1890 (except for one, in 1950) has asked about language characteristics, and its question has always seemed to assume that English is the only language relevant for the aspects of life that take place outside the home. This assumption, though outdated, is somewhat understandable. After all, the bureau’s primary goal in asking this question is not to paint a full and complete portrait of the language proficiencies of Americans but rather to track immigrants’ integration into mainstream American society and to ascertain what services they need, and in what languages. (In October, for instance, the Census Bureau released a list of jurisdictions with large numbers of voters who need voting instructions translated in a language other than English.)

Nonetheless, to better map American language abilities, the census should ask the same question that the European Commission asked in its survey in 2006: Can you have a conversation in a language besides your mother tongue? (The answer, incidentally, dented Europe’s reputation as highly multilingual: only 56 percent of the respondents, who tended to be younger and more educated, said they could.) Until the census question is refined, claims about American monolingualism will almost certainly be overstated.

The celebrated multilingualism of not just Europe but also the rest of the world may be exaggerated. The hand-wringing about America’s supposed linguistic weakness is often accompanied by the claim that monolinguals make up a small worldwide minority. The Oxford linguist Suzanne Romaine has claimed that bilingualism and multilingualism “are a normal and unremarkable necessity of everyday life for the majority of the world’s population.”

But the statistics tell a murkier story. Recently, the Stockholm University linguist Mikael Parkvall sought out data on global bilingualism and ran into problems. The reliable numbers that do exist cover only 15 percent of the world’s 190-odd countries, and less than one-third of the world’s population. In those countries, Mr. Parkvall calculated (in a study not yet published), the average number of languages spoken either natively or non-natively per person is 1.58. Piecing together the available data for the rest of the world as best he could, he estimated that 80 percent of people on the planet speak 1.69 languages — not high enough to conclude that the average person is bilingual.