The government announces a campaign to increase the registration rate, currently 88 percent.
Although there is no military draft, young men are required by law to register for the draft at age 18, but there has been a steady decline in compliance in recent years, the government said Wednesday.
Just 88 percent of young men have registered, with compliance ranging from 95 percent in New Hampshire to 84 percent in Florida to 73 percent in Hawaii.
Lewis C. Brodsky, the draft system's director of public and congressional affairs, said it was unknown why compliance rates varied so widely.
He suggested that low population density might contribute to compliance, with New Hampshire and Maine at the top of the registration chart, but that would not account for the low showing of other states with low population densities like Kentucky and Mississippi.
Another possibility is that large numbers of immigrants may contribute to low registration. That holds true for California and Texas, which have many immigrants and low compliance, but Florida and New York, also with high immigrant populations, have higher levels of compliance.
At a news conference called to announce the start of a campaign to increase the registration rate, Gil Coronado, the Selective Service director, stressed that his agency did not provide names to the Immigration and Naturalization Service.
The government regards registration as an insurance policy of sorts. If war came, men could be drafted faster if they are registered.
The last draftee was inducted in 1973 and the highest level of registration since then was 97.7 percent in 1991.
Coronado said criminal penalties for not registering were rarely imposed, the last case being prosecuted in 1985. Men who did not register would be ineligible for many federal benefits, including student loans, job training and government jobs, and immigrants could not become citizens.
Coronado said that failure to register probably was caused by a growing lack of awareness of the requirement and that it meant there was a risk of "inadvertently creating a permanent underclass of men."