Operating and administrative expenses - improved relative to sales in both 2012 as a whole and the fourth quarter of 2012 versus 2011 as a whole and the fourth quarter of 2011.
Historically, our two largest components of operating and administrative expenses have consisted of employee related expenses (approximately 65% to 70%) and occupancy related expenses (approximately 15% to 20%). The remaining expenses cover a variety of items with selling transportation typically being the largest.
The three largest components of operating and administrative expenses grew as follows for the periods ended December 31 (compared to the comparable periods in the preceding year):
|| Twelve-month period
| Employee related expenses
| Occupancy related expenses
| Selling transportation costs
Employee related expenses include: (1) payroll (which includes cash compensation, stock option expense, and profit sharing), (2) health care, (3) personnel development, and (4) social taxes. The increase in 2012 was driven by the following factors: (1) average employee headcount, measured on a full-time equivalent basis, grew 8.7%, (2) sales commissions grew, (3) bonus amounts related to our growth drivers grew (this includes items such as industrial vending bonuses and manager minimum pay adjustments), and (4) our profit sharing contribution grew. The increase in 2011 was driven by the following factors: (1) employee headcount, measured on a full-time equivalent basis, grew 15.0%, (2) sales commissions grew (this increase was amplified by stronger sales growth relative to 2010, which had a meaningful impact on the commission earned, and higher gross profit margins), (3) total bonuses earned increased due to our profit growth, (4) hours worked per employee grew, and (5) our profit sharing contribution grew.