At regular intervals, congressional Republicans take aim at government surveys, vowing to end or curtail them for being too intrusive. The latest target is the Census Bureau’s American Community Survey.

Begun in 2005 with bipartisan support, the survey polls about three million people a year on family configurations, educational levels, income, insurance coverage and work and living arrangements. It is used to make and evaluate decisions in public policy and business and to understand trends in society. It is also used to analyze and enforce voting rights and to fight discrimination in housing, employment and other areas.

For those reasons, answering the survey is a civic duty, which every adult must do occasionally. But that would change under a bill in the House oversight committee, led by Representative Darrell Issa, a Republican of California. The bill would make answering the survey voluntary, which would make the data less reliable and possibly useless, because fewer people would respond and those who did would not be a valid sample. The result would be a less informed public, a less responsive government and a less fair society.

At an earlier hearing, Mr. Issa was told by experts he convened that the bill was a bad idea, and he didn’t kill it. More recently, he scheduled a committee vote on the bill, only to back down after a coalition of census advocates objected. But Republicans could still try to slip the bill into the upcoming census appropriation, as they have tried in the past. A companion bill in the Senate is sponsored by Rand Paul, a Kentucky Republican. Their very existence is an assertion of ignorance over knowledge, ideology over facts and bias over rights.