text: Our expense related to doubtful accounts as a percentage of revenue for 2002, 2003 and 2004 was .5%, 
  .4% and .3%, respectively. 
  
  As of December 31, 2004, accounts receivable were $268.7 million, net of allowance for doubtful 
  accounts of $18.0 million, resulting in days sales outstanding of 35 days, or 22 days net of deferred revenue. In 
  addition, at December 31, 2004, our trade receivables in excess of 90 days old totaled $16.4 million, or 5.7% of 
  gross receivables outstanding. 
  
  Our expense for self-insurance as a percentage of revenue for 2002, 2003 and 2004 was 5.8%, 7.5% and 
  6.1%, respectively. The increase in self-insurance expense from 2002 to 2003 related to existing claims and was 
  attributable to the expansion of our operations and various changes in estimates as a result of continued 
  negative trends through our 2003 policy year, based on recent actuarial claims experience, expected claims 
  development and medical cost inÖation. 
  
  **Property and Equipment**
  
  The following tables reÖect the activity in our property and equipment accounts for the years ended 
  December 31, 2002, 2003 and 2004 (in millions): 