A multibillion-dollar crime wave is sweeping the country, but the public doesn't seem to notice. Although elaborate scams occasionally grab headlines, insurance fraud remains a largely invisible and ordinary crime - homeowners padding claims for fire and storm damage; doctors overbilling for Medicare; insurance agents pocketing policyowners' premiums. Yet insurance fraud costs the U.S. economy an estimated $80 billion a year, making it the nation's second largest economic crime, after tax evasion. Insurance fraud flourishes in part because insurers often hesitate to challenge dubious claims, and police give top priority to violent crime. Now the insurance industry and government law enforcement agencies are cracking down on fraud - but how much success they will have remains to be seen.