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 22.76% for the second quarter of 2020, compared to 21.87% for the second quarter of 2019. The increase in rate in the second quarter of 2020, compared to the second quarter of 2019, resulted primarily from decreased fuel sales, which have a lower gross margin rate, an increase in our fuel gross margin, growth in our alternative profit stream portfolio, effective negotiations to achieve savings on the cost of products sold, a lower LIFO charge and decreased shrink, transportation and advertising costs, as a percentage of sales, reflecting the significant increase in sales volumes, partially offset by continued investments in lower prices for our customers and a change in our product sales mix, including lower relative sales in higher gross margin categories such as deli/bakery.
Our gross margin rate, as a percentage of sales, was 23.64% for the first two quarters of 2020, compared to 22.06% for the first two quarters of 2019. The increase in rate in the first two quarters of 2020, compared to the first two quarters of 2019, resulted primarily from decreased fuel sales, which have a lower gross margin rate, an increase in our fuel gross margin, growth in our alternative profit stream portfolio, effective negotiations to achieve savings on the cost of products sold and decreased shrink, transportation and advertising costs, as a percentage of sales, reflecting the significant increase in sales volumes, partially offset by continued investments in lower prices for our customers and a change in our product sales mix, including lower relative sales in higher gross margin categories such as deli/bakery.
Our LIFO charge was $23 million for the second quarter of 2020 compared to $30 million for the second quarter of 2019. Our LIFO charge was $54 million for the first two quarters of 2020 compared to $46 million for the first two quarters of 2019. Our LIFO charge reflects an increase in our expected annualized product cost inflation for 2020, primarily driven by grocery, meat and pharmacy.
Our FIFO gross margin rate, which excludes the second quarter LIFO charge, was 22.83% for the second quarter of 2020, compared to 21.98% for the second quarter of 2019. 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 5 basis points in the second quarter of 2020, compared to the second quarter of 2019. This increase resulted primarily from growth in our alternative profit stream portfolio, effective negotiations to achieve savings on the cost of products sold and decreased shrink, transportation and advertising costs, as a percentage of sales, reflecting the significant increase in sales volumes, partially offset by continued investments in lower prices for our customers and a change in our product sales mix, including lower relative sales in higher gross margin categories such as deli/bakery.
Our FIFO gross margin rate, which excludes the first two quarters LIFO charge, was 23.72% for the first two quarters of 2020, compared to 22.13% for the first two quarters of 2019. Excluding the effect of fuel, our FIFO gross margin rate increased 29 basis points in the first two quarters of 2020, compared to the first two quarters of 2019. This increase resulted primarily from growth in our alternative profit stream portfolio, effective negotiations to achieve savings on the cost of products sold and decreased shrink, transportation and advertising costs, as a percentage of sales, reflecting the significant increase in sales volumes, partially offset by continued investments in lower prices for our customers and a change in our product sales mix, including lower relative sales in higher gross margin categories such as deli/bakery.
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.