By Tim Henderson

As the Supreme Court considers a challenge to a citizenship question in the 2020 census, the U.S. Census Bureau will start testing the question’s effect on participation this week.

The bureau announced a test that will go to 480,000 homes, half of which will get the citizenship question. Findings will help determine whether the bureau needs to send out more people to do follow-up interviews if it turns out that the question dampens participation.

The Supreme Court has yet to decide whether the question is allowed, but a majority seemed inclined to support it during arguments in April. The case reached the Supreme Court after the state of New York sued the federal government, saying the question was improperly added, and other states joined the lawsuit.

Opponents and even some internal census research say asking all Americans about citizenship, last done in the 1950 census, would discourage immigrants from participating. High-immigrant states like Arizona, California, Florida and Texas could lose federal funding and seats in Congress if an undercount results. A Supreme Court ruling on the case is expected this month.