OG&A expenses, as a percentage of sales, were 17.37% for the first three quarters of 2019, compared to 16.70% for the first three quarters of 2018. The increase in the first three quarters of 2019, compared to the first three quarters of 2018 resulted primarily from the 2019 OG&A Adjusted Items, the 2018 OG&A Adjusted Item, the effect of decreased supermarket fuel and convenience store sales, which increases our OG&A rate, as a percentage of sales, investments in our digital strategy and increases in hourly associate labor costs attributed to investing in higher wages and other comprehensive benefits to improve employee retention, engagement and customer experience, partially offset by broad based improvement of Restock Kroger cost savings initiatives that drive administrative efficiencies, store productivity and sourcing cost reductions, decreased incentive plan costs and planned real estate transactions during the first quarter of 2019. Excluding the effect of fuel, the 2019 OG&A Adjusted Items and the 2018 OG&A Adjusted Item, our OG&A rate decreased 14 basis points in the first three quarters of 2019, compared to the first three quarters of 2018. This decrease resulted primarily from broad based improvement of Restock Kroger cost savings initiatives that drive administrative efficiencies, store productivity and sourcing cost reductions, decreased incentive plan costs and planned real estate transactions during the first quarter of 2019, partially offset by investments in our digital strategy and increases in hourly associate labor costs attributed to investing in higher wages and other comprehensive benefits to improve employee retention, engagement and customer experience.
During the second quarter of 2019, we accepted an offer to sell an unused warehouse that had been on the market for some time. We used this gain as an opportunity to contribute a similar amount into the UFCW Consolidated Pension Plan, helping stabilize associates’ future benefits. The net impact of these transactions had no effect to OG&A for the first three quarters of 2019.
Rent Expense
Rent expense, as a percentage of sales, remained relatively consistent in both the third quarter and first three quarters of 2019, compared to the same periods in 2018.
Depreciation and Amortization Expense
Depreciation and amortization expense increased, as a percentage of sales, in the third quarter of 2019, compared to the third quarter of 2018. This increase is primarily due to decreased fuel sales, which increases our depreciation expense as a percentage of sales, additional depreciation on capital investments, excluding mergers and lease buyouts, of $3.0 billion, during the rolling four quarter period ending with the third quarter of 2019 and a decrease in the average useful life on these capital investments. Our strategy under Restock Kroger includes initiatives to enhance the customer experience in stores, improve our process efficiency and integrate our digital shopping experience through technology developments. As such, the percentage of capital investments related to digital and technology has grown compared to the prior year, which has caused a decrease in the average depreciable life of our capital portfolio.
Depreciation and amortization expense increased, as a percentage of sales, in the first three quarters of 2019, compared to the first three quarters of 2018. This increase is primarily due to lower fuel sales, which increases our depreciation expense as a percentage of sales, the 2018 Depreciation Adjusted Item, additional depreciation on capital investments, excluding mergers and lease buyouts, of $3.0 billion, during the rolling four quarter period ending with the third quarter of 2019 and a decrease in the average useful life on these capital investments.
Operating Profit and FIFO Operating Profit
Operating profit was $254 million, or 0.91% of sales, for the third quarter of 2019, compared to $647 million, or 2.33% of sales, for the third quarter of 2018. Operating profit, as a percentage of sales, decreased 142 basis points in the third quarter of 2019, compared to the third quarter of 2018, due to increased OG&A and depreciation and amortization expenses, as a percentage of sales, partially offset by a higher gross margin rate.
Operating profit was $1.7 billion, or 1.83% of sales, for the first three quarters of 2019, compared to $2.2 billion, or 2.38% of sales, for the first three quarters of 2018. Operating profit, as a percentage of sales, decreased 54 basis points in the first three quarters of 2019, compared to the first three quarters of 2018, due to increased OG&A and depreciation and amortization expenses, as a percentage of sales, partially offset by a higher gross margin rate.