Aggregated gross profit for the fourth quarter increased 11.0% to $25.2 million, compared to gross profit of $22.7 million in the fourth quarter of the prior year. The Company's aggregated gross profit margin increased 150 basis points to 76.1% in the fourth quarter, compared to a gross profit margin of 74.6% in the fourth quarter of the prior year. The improvement in gross margin was primarily the result of a more favorable speech generating device product mix as well as a higher percentage of sales from software.
Aggregated operating income was $8.0 million in the fourth quarter of 2010, compared to operating income of $9.2 million in the same period a year ago. The fourth quarter of 2010 operating income reflects approximately $1.7 million of equity-based compensation expense, for which expense recognition was accelerated into the fourth quarter of 2010 as a result of the IPO, and approximately $0.5 million of public company related expenses not present in the prior year fourth quarter. Operating expenses also increased from the prior year due to continued investment in sales & marketing and research & development resources. As noted above, the prior year fourth quarter operating income includes $0.7 million of estimated additional operating income as a result of the extra week of sales.
GAAP net income for DynaVox Inc. was $1.0 million, or $0.10 per diluted share, for the period April 28, 2010 through July 2, 2010. For the period April 3, 2010 through April 27, 2010 DynaVox Systems Holdings LLC reported a GAAP net loss of $1.1 million.
Adjusted pro forma net income and adjusted pro forma net income per share, as defined below, were $2.8 million, or $0.09 per diluted share for the fourth quarter, and included $2.1 million of after-tax expenses related to the early retirement of debt from the IPO proceeds, acquisition related costs, and employee severance and other costs. Excluding these expenses, fourth quarter adjusted pro forma net income and adjusted pro forma net income per share would have been $4.9 million or $0.16 per diluted share.