Thanks, Cliff. Good morning, everyone. I'd like to begin by reviewing our first quarter financial results, implied comments on the balance sheet, cash flow statement and taxes. We posted revenue of $1.382 billion for the first quarter, representing a 20% increase year-over-year. Gross margin was 58.1%, a 120 basis point increase from the prior year quarter. The increase was primarily due to product mix in certain segments partially offset by segment mix. Operating expense as a percentage of sales was 36.5%, 330 basis point decrease. Operating income was $298 million, a 51% increase. Operating margin was 21.6%, a 440 basis point increase. Our GAAP EPS was $1.43, pro forma EPS was $1.42.
Next, look at our first quarter revenue by segment and geography. In the first quarter, we achieved double-digit growth in 4 or 5 segments, led by the auto OEM segment with 58% growth, the fitness segment with 40% growth. The marine and outdoor segments also had double-digit growth of 17% and 11%, respectively. By geography, we achieved a double-digit growth in all 3 regions, led by 30% growth in EMEA, followed by 17% growth in Americas and 12% growth in APAC.
Looking next on operating expenses. First quarter operating expense increased by $48 million or 11%. Research and development increased approximately $21 million year-over-year, primarily due to engineering personnel costs. SG&A increased approximately $27 million compared to the prior year quarter, primarily due to increases in personnel-related expenses, including impact of JL Audio.
A few highlights on the balance sheet, cash flow statement and taxes. Ended the quarter with cash and marketable securities approximately $3.3 billion. Cash receivable increased year-over-year due to strong sales, but decreased sequentially to $695 million from a seasonally strong fourth quarter. Inventory decreased year-over-year and sequentially to approximately $1.3 billion. In the first quarter of 2024, we generated free cash flow of $402 million, $170 million increase from the prior year quarter. Capital expenditures for the first quarter of 2024 were $33 million, approximately $14 million lower than the prior year quarter.
In our first quarter of 2024, we paid dividends of approximately $140 million for an effective tax rate of 15.6% compared to 8.8% in the prior year quarter. Increase in effective tax rate is primarily due to the increase in the combined Switzerland tax rate in response to global minimum tax requirements.
That concludes our formal remarks. Paul, can you please open the line for Q&A?