Sales in the Data Center Computing market decreased $10.1 million, or 14.6%, to $59.1 million for the three months ended June 30, 2023 and $26.7 million, or 18.3%, to $118.7 million for the six months ended June 30, 2023 as compared to the same periods in the prior year. The decrease in Data Center Computing market sales was due to slowing demand with some of our data center customers and supply constraints of certain components to meet our full demand.
Sales in the Telecom and Networking market increased $17.6 million, or 46.3%, to $55.7 million for the three months ended June 30, 2023 and $30.4 million, or 41.4%, to $103.8 million for the six months ended June 30, 2023 as compared to the same periods in the prior year. The increase in sales was primarily due to substantially improved material availability, allowing us to partially fulfill outstanding demand from the prior year.
GROSS PROFIT
For the three months ended June 30, 2023, gross profit decreased $15.1 million to $147.1 million, or 35.4% of revenue, as compared to $162.2 million, or 36.8% of revenue, in the same period in the prior year. For the six months ended June 30, 2023, gross profit decreased $4.3 million to $302.2 million, or 36.0% of revenue, as compared to $306.5 million, or 36.6% of revenue, in the same period in the prior year.
The decrease in gross profit as a percentage of revenue for the three and six months ended June 30, 2023 is largely due to the decline in sales, unfavorable product mix, and higher operating costs based on investments made in 2022, partially offset by lower premiums and related recoveries for securing critical parts.
OPERATING EXPENSE
Research and Development
We perform R&D of products to develop new or emerging applications, technological advances to provide higher performance, lower cost, or other attributes that we may expect to advance our customers’ products. We believe that continued development of technological applications, as well as enhancements to existing products and related software to support customer requirements, are critical for us to compete in the markets we serve. Accordingly, we devote significant personnel and financial resources to the development of new products and the enhancement of existing products, and we expect these investments to continue.
R&D expenses increased $3.4 million to $51.4 million for the three months ended June 30, 2023 and increased $11.4 million to $103.0 million for the six months ended June 30, 2023 as compared to the same periods in the prior year. The increase in research and development expense is primarily driven by increased headcount and compensation costs of $3.2 million for the three months ended June 30, 2023 and $7.5 million for the six months ended June 30, 2023, both of which are partially due to the SL Power acquisition.
In addition, we incurred higher program and material costs as we invest in new programs to maintain and increase our technological leadership and provide solutions to our customers’ evolving needs of $0.2 million for the three months ended June 30, 2023 and $3.9 million for the six months ended June 30, 2023.
Selling, General, and Administrative
Our selling expenses support domestic and international sales and marketing activities that include personnel, trade shows, advertising, third-party sales representative commissions, and other selling and marketing activities. Our general and administrative expenses support our worldwide corporate, legal, tax, financial, governance, administrative, information systems, corporate development, and human resource functions.
Selling, general and administrative (“SG&A”) expenses increased $0.6 million to $55.6 million for the three months ended June 30, 2023 and increased $6.6 million to $111.0 million for the six months ended June 30, 2023 as compared to the same periods in the prior year. The increase in SG&A is primarily related to increased headcount and associated costs, including sales commissions and stock-based compensation.