NEW YORK (Reuters) - Progressive Corp (PGR.N: Quote, Profile, Research), the No. 3 U.S. auto insurer, said on Wednesday that monthly earnings were 20 percent lower in April, as business fell and costs rose.

Net income in April dropped to $108.9 million, or 16 cents a share, from $136.7 million, or 19 cents a share in April 2007.

Progressive said net premiums written fell 2 percent to $1.4 billion, while net premiums earned were down 3 percent at $1.3 billion. April policies in force in personal lines,including autos, rose 3 percent to 10.3 million, while commercial auto policies in force rose 6 percent to 552,200, the company said.

The company's combined ratio -- a measure of how much is spent for every dollar of premium earned -- gained 2.9 points to 91.7. The lower the figure, the better the insurer has been at keeping claims and other business costs in check.

(Reporting by Lilla Zuill, editing by Maureen Bavdek)