Overall selling, general and administrative ("SG&A") expenses increased $12.0 million, or 43%, from $28.0 million in 2009 to $40.0 million for the twelve months ended December 31, 2010, largely due to the Bigler and SLE writeoffs. As a percentage of revenue, SG&A increased from 8.2% in 2009 to 12.5% in 2010.
The Company's days of sales outstanding increased slightly to 56 days at December 31, 2010, from 55 days at December 31, 2009. Bad debt expense was approximately 3.3% and 0.2% of revenue for the years ended December 31, 2010 and 2009, respectively.
Long-term debt, net of current portion, decreased 95%, or $5.8 million, from $6.1 million at December 31, 2009 to $0.3 million at December 31, 2010. As a percentage of stockholders' equity, long-term debt decreased to 0.4% from 7.7% at these dates. The decrease in long-term debt primarily relates to the reclass of our credit facility to a current liability during the second quarter as a result of covenant defaults, all of which have now been waived. Cash on hand at December 31, 2010 totaled $49,000 and availability under the Company's credit facility totaled $5.4 million resulting in total liquidity of $5.5 million. At December 31, 2010, the amount outstanding on the Wells Fargo Credit Facility was $18.7 million compared to $6.0 million at December 31, 2009. The Company has been in negotiations with Wells Fargo since the fourth quarter of 2010 to increase availability under its credit facility.
ENGlobal's employee count decreased to approximately 2,000 for the quarter ended December 31, 2010. ENGlobal averaged 174,000 billable hours per two-week period during the fourth quarter 2010, an 11% increase, when compared to 157,000 billable hours in the same period in 2009. The fourth quarter 2010 average represents a 5% increase over 166,000 billable hours in the third quarter 2010. The Company's overall utilization percentage was approximately 91% for the fourth quarter 2010, compared with approximately 89% for the comparable period of 2009.