environments. HiP’s products and business relationships enhance Graco’s position in the oil and natural gas industry and complement Graco’s core competencies of designing and manufacturing advanced flow control technologies. Results of HiP operations have been included in the Company’s Process segment from the date of acquisition.
On January 2, 2015, the Company acquired White Knight Fluid Handling (“White Knight”) for $16 million cash and a commitment for additional consideration if future revenues exceed certain thresholds, initially valued at $8 million. The maximum payout is not limited. White Knight designs and manufactures high purity, metal-free pumps used in the production process of manufacturing semiconductors, solar panels, LED flat panel displays and various other electronics. Results of White Knight operations have been included in the Company’s Process segment from the date of acquisition.
In October 2014, we acquired the stock of Alco Valves Group (“Alco”) for £72 million cash. Alco is a United Kingdom based manufacturer of high quality, high pressure valves used in the oil and natural gas industry and in other industrial processes. Alco’s products and business relationships enhance Graco’s position in the oil and natural gas industry and complement Graco’s core competencies of designing and manufacturing advanced flow control technologies. Results of Alco operations have been included in the Company’s Process segment from the date of acquisition.
In January 2014, the Company paid $65 million cash to acquire QED Environmental Systems (“QED”), a manufacturer of fluid management solutions for environmental monitoring and remediation, markets where Graco had little or no previous exposure. Results of operations have been included in the Company’s Process segment from the date of acquisition.
The Company completed other business acquisitions in 2015, 2014 and 2013 that were not material to the consolidated financial statements.
Results of Operations
Net sales, operating earnings, net earnings and earnings per share were as follows (in millions except per share amounts):
Diluted Net Earnings per Common Share
Net sales grew by 5 percent compared to 2014. At consistent currency translation rates, sales increased 10 percent, including growth from acquired operations of 6 percentage points and organic growth of 4 percentage points.
More than 90 percent of our organic growth at consistent translation rates in 2015 came from our Contractor and Industrial businesses in the Americas. Our Process segment has some exposure to oil and natural gas end markets, which limited organic growth at consistent translation rates in that segment to 1 percent.
Changes in currency translation rates reduced sales, operating earnings, and net earnings by approximately $58 million, $32 million and $20 million, respectively.
Acquired operations contributed $67 million of incremental sales in 2015.
Gross profit margin, expressed as a percentage of sales, was 53 percent for the year, slightly lower than 2014, mostly due to changes in currency translation rates. Favorable effects of realized pricing and lower material costs offset the impact of lower average gross margin rates of acquired operations.
Operating expenses increased $25 million (7 percent) over 2014. Decreases from changes in currency translation rates ($16 million) partially offset increases from acquired operations ($27 million), spending related to regional and product expansion initiatives ($4 million) and unallocated corporate expenses ($5 million).
Investment in new product development was $59 million or 4½ percent of sales in 2015, consistent with 2014 expense as a percentage of sales.
The effective tax rate for 2015 was 27 percent, down from 28 percent in 2014 primarily due to a change in our assertion with respect to the reinvestment of foreign earnings.
Net earnings include $141 million of after-tax gain on the sale of Liquid Finishing business assets and $42 million of dividends received prior to the sale. Dividends from Liquid Finishing totaled $28 million in 2014.
Share repurchases totaled 3.9 million in 2015, driving a reduction of 2.7 million shares in the weighted average shares outstanding for diluted earnings per share.