Now, let's focus on construction and forestry on Slide 15. Net sales for the quarter, up $2.99 billion, were up 100% compared with last year driven by strong demand for construction and forestry equipment as well as well as by the acquisition of Wirtgen, which contributed 77% of the positive improvement. Third quarter operating profit was $281 million benefiting from higher shipment volumes, Wirtgen acquisition and lower warranty expense partially offset by higher production cost and higher sales incentive expenses. C&F operating margins were 9.4% for the quarter, but 10.5% excluding Wirtgen. Moving to Slide 16, the economic environment for the construction, forestry and road-building industries look strong and continue to support increased demand for new and used equipment.
For the year, U.S. GDP is forecast to grow at about 3%, which is above the 20-year average. Correspondingly, U.S. housing demand remains solid with housing starts expected to be about 1.3 million units for 2018 as inventories of new and existing homes available-for-sale remain at 36-year lows. Residential construction continues to serve as an important indicator for earthmoving equipment sales and current housing demand levels suggest continued growth in the segment. Additionally, construction investment in the U.S. is forecast to grow 3.8% for the year led largely by increased activity in oil and gas. With oil prices now forecast to average about $67 a barrel for the year, backlogs for many oilfield contractors are extending through 2019, which is supported for further equipment demand. Lastly, global transportation investment this year is forecast to grow about 6% driving increased demand for road construction equipment, such as milling machines, rollers and asphalt pavers, which are all important product lines for Wirtgen. These positive economic indicators are reflected in a strong order book, which is now extending well into 2019.
Moving to the C&F outlook on Slide 17, Deere's construction and forestry sales are now forecast to be up about 81% in 2018 as a result of stronger demand for equipment as well as the acquisition of Wirtgen. The net sales forecast includes about $3.15 billion attributable to Wirtgen, which was adjusted downward due entirely to FX. The forecast for global forestry market is up about 10% as a result of improvement in sales in the U.S. and Canada and strong demand for cut-to-length products in Europe and Russia. C&F's full year operating margin is projected to be about 8.5%, which includes the negative impact of purchase accounting and acquisition costs from Wirtgen. Excluding Wirtgen, C&F projects operating margins to be about 10.5%. Wirtgen continues to perform as expected with strong backlogs and operating margins now forecast to achieve the high-end of our 3% to 4% guidance.
Let's move now to our financial services operations. Slide 18 shows the provision for credit losses as a percentage of the average owned portfolio. Financial forecast for 2018 shown on the slide contemplates a loss provision of about 15 basis points, 6 basis points lower than our previous forecast. This will put loss provisions for the year below the 10-year average of 25 basis points and the 15-year average of 27 points.
Moving to Slide 19, worldwide financial services net income attributable to Deere & Company was $151 million in the third quarter. The results for the quarter included about $4 million in net tax reform related charges arising from the re-measurement of deferred tax asset and deemed earnings repatriation. Excluding tax reform related items, adjusted net income in the third quarter was $148 million, up about 13% compared to the same quarter last year. For the full year in 2018 net income is forecast to be about $815 million. Excluding the impacts of the previously mentioned tax reform related items adjusted net income is forecast to be $583 million. Beyond 2018, effective tax rates for John Deere Financial are forecast to be between 24% and 26%.
Slide 20 outlines receivables and inventories. For the company as a whole receivables and inventories ended the quarter up $3.8 billion. In the C&F division the majority of the increase is attributable to Wirtgen, while for ag, the increases due to higher sales. By the end of fiscal year 2018 receivables and inventories are expected to increase about $2.5 billion from 2017 levels, driven largely by the inclusion of Wirtgen as well as the higher sales across the company.
Slide 21 shows the cost of sales as a percentage of net sales. Cost of sales for the third quarter was 77%. Our 2018 cost of sales guidance is about 76% of net sales, unchanged from previous guidance.
When modeling 2018 keep these unfavorable impacts in mind higher production costs such as freight and material costs and higher incentive compensation costs. On the favorable side, we expect price realization of about one point and a more positive product mix.
Now, let's look at some additional details. With respect to R&D expense on Slide 22, R&D was up about 23% in the third quarter. Approximately 12% of the increase relates to the acquisitions of Wirtgen and Blue River Technology. Our 2018 forecast calls for R&D to be up about 21% with acquisition related activity accounting for nine points of the increase and currency translation of one point. The balance of the R&D increase largely relates to strategic investments in large ag and precision ag that helps drive growth for these key areas. Moving now to Slide 23, SA&G expense for the equipment operations was up 19% in the third quarter with acquisition related activities and incentive compensation accounting for most of the change. Our full year 2018 forecast for SA&G expense is up about 16%. Excluding acquisition related expenses, SA&G is forecast to be flat for the year.
Turning to Slide 24, the equipment operations tax rate was 24% in the third quarter, which included a favorable adjustment of approximately $62 million arising from tax reform related net deferred tax asset re-measurement and deemed earnings repatriation. Fourth quarter, the effective tax rate is expected to be in the range of 25% to 27%, which implies a full year effective tax rate of approximately 55%. For 2019, Deere's full year effective tax rate is projected to be between 25% and 27%.
Slide 25 shows our equipment operations history of strong cash flow. Cash flow from the equipment operations is now forecast to be about $3.5 billion in 2018 compared to previous guidance of $3.8 billion. The decrease is for — the decrease in forecast largely relates to an anticipated increase in working capital. The company's financial outlook is on Slide 26. Fourth quarter equipment sales are forecast to be up about 21% compared with the same quarter last year. Our full year outlook now calls for net sales to be up about 30% which includes about one point of price realization and 12 points for the acquisition of Wirtgen. Finally, our full year 2018 GAAP net income forecast is now about $2.36 billion. The full year net income forecast includes charges of $741 million resulting from tax reform related net deferred tax asset re-measurement and deemed earnings repatriation. Excluding the impact of these items, adjusted net income is forecast to be about $3.1 billion.
I will now turn the call over to Raj Kalathur for closing comments. Raj?