J. Schlotman
Analyst · Morgan Stanley
Thanks, Rodney, and good morning, everyone. We are pleased with our net adjusted operating earnings per diluted share result of $0.48 for the third quarter. Strong fuel margins and continued execution of Restock Kroger contributed to this result. We continue to make several Restock Kroger investments in the third quarter. These included investments in price, especially in support of Our Brands and in space optimization, store remodels and technology enhancements.
Part of these investments will allow customers to buy Anything, Anytime, Anywhere from Kroger. As we discussed at our Investor Conference, space optimization is a massive undertaking, and we continue to expect to end the year with 600 stores completed. Our ID sales for the third quarter were in line with our expectation. ID sales were led by natural foods, pharmacy, seafood, produce and deli departments.
Looking at gross margin. We were pleased to see that our shrink rate continued to improve during the third quarter compared to the previous year. The gross margin rate reflects the timing and size of company's price investments compared to a year ago, rising transportation costs and growth of the specialty pharmacy business, which is a high-sales, low-margin rate business that generates strong gross profit dollars.
Keep in mind that last year in the third quarter, our gross margin rate was higher than our typical run rate. For the third quarter in 2018, gross margin, excluding fuel, was actually higher than the second quarter of 2018. These fluctuations illustrate how results in a given quarter can vary based on the cadence of the investments we make in the business.
Part of our investments this year support the Our Brand strategy where we continue to offer high-quality products at a great value. The improvement in unit movement in the quarter demonstrates these investments are resonating with customers. We intended to continue investing in price to drive unit growth while also delivering on the bottom-line for our shareholders.
We are pleased that OG&A costs decreased by 20- basis points as a rate of sales. The significant improvements we are seeing from our focus on reducing store associate turnover is contributing to this positive movement. We continue to focus on productivity and waste and improvements in our cost to fill prescriptions and increased adoption of self-scan contributed to this improvement. Our investments in Restock Kroger in redefining the customer experience, partnering for customer value and developing talent will be paid for by cost of goods savings, strong ID sales and productivity gains. This will contribute to generating $400 million in incremental FIFO operating profit through 2020.
Now for an update on our fuel -- retail fuel performance during the third quarter. Our cents per gallon fuel margin was approximately $0.261 compared to $0.249 in last year's third quarter. The average retail price of fuel was $2.81 compared to $2.46 in the same quarter last year. We expect our tax rate for 2018 to be approximately 23%. Excluding the 2018 adjustment items, Kroger expects its tax rate to be approximately 21%. These rates reflect the third quarter adjustment related to a regular IRS audit. The IRS audit resulted in a reduction in prior year tax deductions at pretax reform rates and future tax deductions at post-tax reform rates.
Our financial strategy is to use free cash flow to drive growth while also maintaining our current investment grade debt rating and returning capital to shareholders. We continually balance the use of cash flow to achieve these goals. Over the last 4 quarters, we used cash to invest the combined $589 million in Ocado securities and Home Chef; contribute an incremental $185 million pretax through a company-sponsored pension plan; $467 million to satisfy withdrawal obligations to the Central States Pension Fund; repurchase 91 million common shares for $2.3 billion, which includes $1.2 billion repurchased with after-tax proceeds from the sale of Kroger's convenience store business under an accelerated stock repurchase plan. We paid $435 million in dividends and we invested $3 billion in capital, excluding mergers, acquisitions and purchases of leased facilities. At the end of the third quarter, we had approximately $546 million remaining under the current share repurchase authorization.
We remain committed to generating the $6.5 billion of Restock free cash flow by 2020 as part of our Restock Kroger Plan. We have working capital improvements built into this guidance and off to a great start with $100 million improvement in net operating capital -- net operating working capital, so far, this year. Kroger's net total debt to adjusted EBITDA ratio on a 52-week basis is 2.72. Our net total debt to adjusted EBITDA ratio target is 2.3 to 2.5x, and we remain committed to bringing the leverage ratio back into the target range.
We are investing an incremental $500 million in our associates in wages, training and development over the next 3 years through Restock Kroger. This will be in addition to our continued efforts to rebalance pay and benefits while also focusing on certifications and performance incentives, career opportunities and training.
In March, we also announced investing a portion of our tax savings in our educational assistance program, Feed Your Future, and an increased 401(k) match for nonunion associates. The average hourly rate for our store associates is more than $18 per hour when you factor in our comprehensive benefits that many of our competitors don't offer. We recently ratified a new labor agreement with the UFCW covering more than 13,000 Kroger associates in Columbus, Ohio. The agreement raises starting wages and accelerates wage progressions after 1 year of service. We are currently negotiating with UFCW for contracts covering store associates at Smith's in Albuquerque and Fred Meyer in Portland.
Our objective in every negotiation is to find a fair and reasonable balance between competitive costs and compensation packages that provide solvent wages, good quality affordable health care and retirement benefits for our associates. We continue to strive to make our overall benefits package relevant to today's associates.
Our financial results continue to be pressured by inefficient health care and pension costs, which some of our competitors do not face. We continue to communicate with our local unions and the international unions, which represent many of our associates on the importance of growing our business in a profitable way, which will help us create more jobs and career opportunities and enhance job security for our associates.
Turning now to guidance for the remainder of 2018. We continue to expect identical sales growth, excluding fuel, in the second half to be similar to the first half results. We updated our GAAP net earning guidance to $3.80 to $3.95 per diluted share for 2013 (sic) [ 2018 ] from the previous range of $3.88 to $4.03. The change in GAAP guidance is due to the third quarter market value adjustment of $0.09 per diluted share for Kroger's investment in Ocado shares and does not reflect any future changes in the market value of those shares because those cannot be predicted.
On an adjusted basis, we maintained our net operating earnings guidance range of $2.00 to $2.15 per diluted share for 2018, and keep in mind that fiscal 2017 included an extra week. We continue to expect capital investments, excluding mergers, acquisitions and purchases of leased facilities, to be approximately $3 billion for 2018.
And now I'll turn it back to Rodney.