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 22.03% for the third quarter of 2023, compared to 21.37% for the third quarter of 2022. 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 third quarter of 2023, compared to the third quarter of 2022, resulted primarily from a decreased LIFO charge, an increase in our fuel gross margin, Our Brands performance, effective negotiations to achieve savings on the cost of products sold, lower transportation costs, as a percentage of sales, and the effect of our terminated agreement with Express Scripts, partially offset by higher shrink and advertising costs, as a percentage of sales, and increased promotional price investments.
Our gross margin rate, as a percentage of sales, was 22.08% for the first three quarters of 2023, compared to 21.34% for the first three quarters of 2022. 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 three quarters of 2023, compared to the first three quarters of 2022, resulted primarily from a decreased LIFO charge, an increase in our fuel gross margin, Our Brands performance, our ability to effectively manage product cost inflation through strong sourcing practices, lower transportation costs, as a percentage of sales, and the effect of our terminated agreement with Express Scripts, partially offset by higher shrink, as a percentage of sales, and increased promotional price investments.
Our LIFO charge was $29 million in the third quarter of 2023, compared to $152 million in the third quarter of 2022. Our LIFO charge was $131 million in the first three quarters of 2023, compared to $392 million in the first three quarters of 2022. Our decreased LIFO charge reflects our lower expected annualized product cost inflation for 2023 compared to 2022.
Our FIFO gross margin rate, which excludes the LIFO charge, was 22.11% in the third quarter of 2023, compared to 21.81% in the third quarter of 2022. 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 3 basis points in the third quarter of 2023, compared to the third quarter of 2022. 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 Our Brands performance, effective negotiations to achieve savings on the cost of products sold, lower transportation costs, as a percentage of sales, and the effect of our terminated agreement with Express Scripts, partially offset by higher shrink and advertising costs, as a percentage of sales, and increased promotional price investments.
Our FIFO gross margin rate, which excludes the LIFO charge, was 22.19% in the first three quarters of 2023, compared to 21.68% in the first three quarters of 2022. Excluding the effect of fuel, our FIFO gross margin rate increased 20 basis points in the first three quarters of 2023, compared to the first three quarters of 2022. 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 Our Brands performance, our ability to effectively manage product cost inflation through strong sourcing practices, lower transportation costs, as a percentage of sales, and the effect of our terminated agreement with Express Scripts, partially offset by higher shrink, as a percentage of sales, and increased promotional price investments.