Gross profit margin, expressed as gross profit as a percentage of net sales, decreased 26 basis points for the three months ended June 30, 2012 to 29.9% from 30.2% for the comparable prior year period. The decrease was largely due to a decrease in gross profit margin in the video and appliance categories, partially offset by a favorable sales mix. During the fiscal second quarter of the prior year, the Company experienced an overall reset of gross profit margin rates in the video category. As the Company has not lapped this reset, gross profit margin rates experienced pressure during the first fiscal quarter of the current year. Appliances also experienced a slight decline in gross profit margin as a result of initiatives to grow market share in the category and increased promotional activity, partially offset by a shift in the product mix within the category to products with higher gross profit margins. The computing and mobile phones category experienced an increase in gross profit margin due to mobile phones, which the Company did not offer in the comparable prior year period. These declines were also offset by an increase in gross profit margin rate in the other category, which was primarily due to increases in furniture and mattresses.
SG&A expense, as a percentage of net sales, increased 32 basis points for the three month period ended June 30, 2012 compared to the prior year period. The increase in SG&A as a percentage of net sales was largely a result of increases in employee benefit expenses due to increased health insurance costs, in addition to the deleveraging effect of the comparable store sales decline. This increase was partially offset by slight decreases in other SG&A accounts as a result of cost control measures implemented during the quarter.
Net advertising expense, as a percentage of net sales, increased 96 basis points during the three months ended June 30, 2012 compared to the prior year period. The increase as a percentage of net sales was driven largely by greater promotional activity to drive market share and the deleveraging effect of the comparable store sales decline.