CENSUS FIGURES are important to cities and states not simply because they provide information that is helpful to social scientists and city planners, but also because population determines political representation and federal grant formulas. It is a blow to a state's pride to lose a congressman, and it is a blow to the pocketbook to have federal assistance cut because aid formulas change to reflect census data. It is no wonder, then, that a number of cities are reluctant to accept statistics that show dramatic drops in population.

The 1980 census figures are as controversial as any in history. They show a dramatic shift of population to the Sun Belt and out of the Northeast and Midwest. Several cities have sued the Census Bureau, challenging the accuracy of the count and specifically asking to see raw data collected by the bureau in order to challenge the findings.

The Supreme Court has decided two of these cases in a manner that will probably doom all the others. Essex County, N.J.--which includes the city of Newark--and Denver had gone to court to get census information from the bureau that, they hoped, would substantiate their claims that their populations had been undercounted. The court firmly and finally told them that census information is confidential by statute and that the master address lists they sought would not be released. Only Congress, wrote the chief justice for a unanimous court, can change the law. Without this data, of course, the cities will not be able effectively to challenge the census findings.

The decision was a good one, and Congress should not change the law. It is important, if valid statistics are to be collected, that citizens be confident that their answers to the census takers remain confidential. Questions of age, race, education, relationship to housemates, income and the state of plumbing in one's home are not exactly matters everyone wants to chat about. Congress recognized that an accurate census and valid statistics could only be achieved with the cooperation of the public, and confidentiality was assured in order to get that cooperation.

There is also something to be said for accepting the finality and integrity of the census. Money and power are allocated according to these findings, and the temptation to challenge them ad infinitum is great. The Census Bureau made an unprecedented effort before the 1980 count to encourage public cooperation, particularly in minority areas. Cities have all been given an opportunity to review preliminary data and correct gross errors. Now it's time to accept the word of the experts on the numbers and get on with the redistricting.