Gross Margin, LIFO and FIFO Gross Margin
We define gross margin as sales minus merchandise costs, including advertising, warehousing, and transportation. Rent expense, depreciation and amortization expense, and interest expense are not included in gross margin.
Our gross margin rate, as a percentage of sales, was 22.56% for the second quarter of 2024, compared to 21.79% for the second quarter of 2023. This increase in rate was achieved while maintaining competitive prices and helping customers manage their budgets. The increase in rate in the second quarter of 2024, compared to the second quarter of 2023, resulted primarily from decreased fuel sales, which have a lower gross margin rate, an increase in our fuel gross margin, favorable product mix in our grocery business including Our Brands, lower shrink and our ability to effectively manage product costs through strong sourcing practices, partially offset by lower pharmacy margins.
Our gross margin rate, as a percentage of sales, was 22.48% for the first two quarters of 2024, compared to 22.10% for the first two quarters of 2023. This increase in rate was achieved while also investing in price to maintain a competitive price position and deliver greater value for our customers. The increase in rate in the first two quarters of 2024, compared to the first two quarters of 2023, resulted primarily from decreased fuel sales, which have a lower gross margin rate, an increase in our fuel gross margin, favorable product mix in our grocery business including Our Brands, a decreased LIFO charge and our ability to effectively manage product costs through strong sourcing practices, partially offset by lower pharmacy margins and increased promotional price investments.
Our LIFO charge was $21 million in the second quarter of 2024, compared to $4 million in the second quarter of 2023. Our LIFO charge was $62 million in the first two quarters of 2024, compared to $102 million in the first two quarters of 2023. Our decreased LIFO charge for the first two quarters of 2024, compared to the first two quarters of 2023, was due to our lower expected annualized product cost of inflation for 2024 compared to 2023.
Our FIFO gross margin rate, which excludes the LIFO charge, was 22.63% in the second quarter of 2024, compared to 21.81% in the second quarter of 2023. Our fuel sales lower our FIFO gross margin rate due to the very low FIFO gross margin rate, as a percentage of sales, of fuel sales compared to non-fuel sales. Excluding the effect of fuel, our FIFO gross margin rate increased 42 basis points in the second quarter of 2024, compared to the second quarter of 2023. This increase in rate was achieved while maintaining competitive prices and helping customers manage their budgets. This increase resulted primarily from favorable product mix in our grocery business including Our Brands, lower shrink and our ability to effectively manage product costs through strong sourcing practices, partially offset by lower pharmacy margins.
Our FIFO gross margin rate, which excludes the LIFO charge, was 22.55% in the first two quarters of 2024, compared to 22.23% in the first two quarters of 2023. Excluding the effect of fuel, our FIFO gross margin rate increased 14 basis points in the first two quarters of 2024, compared to the first two quarters of 2023. This increase in rate was achieved while also investing in price to maintain a competitive price position and deliver greater value for our customers. This increase resulted primarily from favorable product mix in our grocery business including Our Brands and our ability to effectively manage product costs through strong sourcing practices, partially offset by lower pharmacy margins and increased promotional price investments.
Operating, General and Administrative Expenses
OG&A expenses consist primarily of employee-related costs such as wages, healthcare benefit costs, retirement plan costs, utilities and credit card fees. Rent expense, depreciation and amortization expense, and interest expense are not included in OG&A.
OG&A expenses, as a percentage of sales, were 17.36% in the second quarter of 2024 and 20.49% in the second quarter of 2023. The decrease in the second quarter of 2024, compared to the second quarter of 2023, resulted primarily from the 2023 Second Quarter OG&A Adjusted Items and continued execution of broad-based cost savings initiatives that drive administrative efficiencies, including store productivity, partially offset by the effect of decreased fuel sales, which increases our OG&A rate, as a percentage of sales, planned investment in associates, increased incentive plan costs, hurricane related costs, an increase in costs due to the severity of general liability claims and the 2024 Second Quarter OG&A Adjusted Item.