THE noisy debate over how to fix America’s immigration system is mainly about the large and rapidly growing Hispanic minority. Behind this hums a quieter debate over how they should be counted. Every ten years the American government conducts a census of its citizens. Hispanics present a particular challenge.

According to guidelines laid down by the federal Office of Management and Budget in 1977, “Hispanic” is an ethnicity, not a race. Someone of Hispanic origin may belong to any of the five officially recognised races: white, black, Asian, American Indian or Pacific Islander (or any combination of these). The census form reflects this distinction.

This, however, is not how many American Hispanics have come to see themselves. In 2010, the last time a count was carried out, many were puzzled by a form that asked them first to declare whether or not they were of Hispanic origin, and then to say what race they belonged to. Half identified themselves as white. But over a third ticked a box marked “Some other race”. As a result, “some other” emerged as America’s third-largest racial grouping.

This frustrates the head-counters. So for the next count, in 2020, the Census Bureau is considering collapsing the two ethnicity and race questions into a single “race or origin” inquiry (it may also drop the anachronistic term “Negro”). This will allow people who identify themselves solely as Hispanic to declare themselves as such (though they may tick extra boxes, such as “black” or “white”, if they like).

Such a change, say officials, would not mean that “Hispanic” is now to be considered a new racial category. Still, the widespread reporting of Hispanic-specific data, acknowledges Roberto Ramirez at the Census Bureau, means that in some respects “Hispanic” has become a de facto race.

Some are sceptical about the proposal. Rubén Rumbaut, a sociologist at the University of California, Irvine, accepts the need for good data but says the bureau is thinking about race in 18th-century terms. Hispanic identity in America, he adds, is a “Frankenstein’s monster” that has taken on a life of its own.

The ethnic origins of some previous waves of immigrants have evaporated over time: Italians, Germans and Russians, dismissed by Benjamin Franklin in 1751 as of “swarthy Complexion”, are now, for the most part, just white. Similar forces may be at play today: last year the Pew Hispanic Centre found that among Hispanics of the third generation or above, almost half preferred to call themselves “American”.

Moreover, Hispanic identity is hardly fixed, notes David Morse of New American Dimensions, a market-research firm. Marketing to American Hispanics took off in the 1980s, spurred by Spanish-language media like Univision, a television network. But today savvy marketers must find subtler ways to appeal to a still-distinct but more assimilated Hispanic audience.

These difficulties are nothing new. The racial categories “quadroon” and “octoroon” once appeared on the census form. More recently officials were (briefly) alarmed when data appeared to show a sudden leap in the Hispanic populations of Kansas and Missouri. Residents of those states had decided a box marked “Central American” on the 1970 census form must have been intended for them.