Rupert Cornwell: US gets ready to sit up and be counted

Out of America: Much hinges on the outcome of the 2010 national census – from voting rights to government aid

It may be the biggest mobilisation of American government in time of peace. Unlike most mobilisations, however, this one begins in earnest on a Sunday, with a commercial spot during this evening's Golden Globes extravaganza, Hollywood's annual curtain-raiser to the Oscars. The ad features the actor Ed Begley, playing a movie director whose new project is to create a portrait "of every man, woman and child in this beautiful country of ours". Welcome to the US national census of 2010.

Here more than anywhere, the census is a very big deal, stipulated by the founding fathers no less. An "enumeration", it is called in Article I, Section 2 of the US constitution, that "shall be made... within every subsequent term of 10 years, in such manner as Congress shall by law direct". The first census was carried out in 1790. This year's exercise will be the 23rd of its kind – and a great deal will be riding on it.

Over $450bn of federal spending is allocated according to the returns, while the numbers of congressional districts in each state, and thus the number of that state's electoral college votes in presidential elections, are adjusted according to the census.

By past standards the actual questionnaire this time is pretty short – just 10 questions covering such basics as age, sex, race, ethnic origin and type of dwelling. Forms will sent to each household in the land, to be completed by every person in the household, in time for 1 April, Census Day proper, and then mailed back to the census organisation. If no return is provided, an interviewer will come to the house, up to six times if necessary, to collect the missing information in person.

This time, as the country slowly emerges from recession, the census will be especially valuable, to businesses and individuals alike. Cash-squeezed companies will rely even more than usual on free census data to shape their marketing strategies, while for a few months hundreds of thousands of people will have temporary work with the census, that pays $15 to $20 (£9-£12) an hour – not a sum to be sniffed at, when the minimum wage is $7.

But the fuss reflects something else as well: the American love of, nay obsession with, numbers and statistics. Europeans tend to be more interested in the psychological truth. Americans spend their lives seeking numerical, scientific truth. Examples are everywhere, from the blindingly obvious survey findings, especially regarding health issues, with which radio and TV news stations fill empty moments, to the statistics that drown every sport, and the national predilection for lists and rankings of every kind.

No matter that the figures can be dodgy – for instance, budget predictions that stretch ahead a decade, when in reality no one has a clue what will happen next month. No health care legislation could be addressed until the non-partisan Congressional Budget Office has delivered its verdict on its financial impact of each particular proposal, even though the CBO freely admits its estimates are no more than guesswork.

You see it too in the American approach to intelligence and spying – the accumulation of vast masses of quantifiable information through intercepts, satellites and so on, but an unease with messier human intelligence. The result is census-sized mountains of data, that in practice are often unmanageable.

And the real census isn't perfect either. Cities, in particular, with their migrant populations, sublets and reconfigurations of residential buildings, tend to be under-counted. A few years ago Washington DC appealed against the 2000 census and had its population increased by 30,000 to 580,000 – no small matter if that meant a 5 or 6 per cent increase in federal funding. This year, foreclosures are another complicating factor. Census workers will have to visit millions of homes to see if they really are empty.

More serious, censuses tend to undercount African Americans (by an estimated three million, or 1 per cent of the total population in 2000), and Hispanics by an even larger number. By law census returns are confidential. But many people without proper papers refuse to provide information about themselves that they fear will be handed over to the immigration authorities.

In an effort to soften that hostility, some Latino groups have been using the Christmas story to sell the 2010 census. "Asi nacio Jesus, This is how Jesus was born," proclaims a poster featuring the star over Bethlehem, "Mary and Joseph participated in the census" (organised, of course, by Caesar Augustus, not the US government).

Predictably though, that initiative backfired, as Hispanic priests complained the poster violated the separation of church and state. Other objections have included the form's use of the word "negro" alongside "black" and "African American" as a racial category – even though census organisers insist that "negro" has featured in every census for the past 100 years, and that last time, more than 50,000 people specifically wrote in "negro" when asked to give further details of their race.

Then there's the problem of prison populations (no small matter when one in 100 adults in the US are behind bars). The census treats prisoners as residents of the district where their jail is, not of where they used to live, often inner-city neighbourhoods. Under the formula for allocating federal aid, this means that more money goes to rural areas where most prisons are found, and less to cities where it is really needed, and might even have kept some from becoming criminals in the first place. But in the great census mobilisation, these are mere quibbles. Let America's decennial mega-fix of statistics begin.