An improving auto market in the United States appears to be boosting the fortunes of satellite radio broadcaster Sirius XM, as the company announced it closed out 2009 with 18,722,758 subscribers, including a net addition of 257,028 subscribers in the fourth quarter.

Even so, the company still chocked up a net loss of subscribers for the year, having finished 2008 with 19,003,856 subs. That overall annual drop was attributed in large part to a brutal decline in U.S. auto sales during the first half of 2009. Sales began to recover in late summer as the federally subsidized Cash for Clunkers program and stabilization of the economy's financial sector contributed to an improving auto sales trend line across the second half.

Sirius XM says it plans to release full-year 2009 financial results in February.