pre_text: ITEM 6. SELECTED FINANCIAL DATA Financial Highlights (dollars in thousands, except per share amounts) (1) During fiscal 2019, the Company recorded $7.0 million of special tax expense in accordance with regulations under U.S. Tax Reform, and reasserted that certain historical undistributed earnings of two foreign subsidiaries will be permanently reinvested, resulting in a $10.5 million benefit. (2) During fiscal 2019, the Company recorded $1.7 million, $1.5 million net of taxes, in restructuring costs, which are included in operating income. (3) During fiscal 2018, the Company recorded $85.9 million of non-recurring income tax expense due to the enactment of U.S. Tax Reform and paid a $13.5 million one-time non-executive employee bonus. (4) During fiscal 2016, the Company recorded $7.0 million in restructuring costs and $5.2 million in selling and administrative expenses, which are included in operating income. The $7.0 million was largely related to the Company's closure of its manufacturing facility in Fremont, California, and the partial closure of its Livingston, Scotland facility. The $5.2 million was related to accelerated share-based compensation expense recorded pursuant to the retirement agreement with the Company's former Chief Executive Officer. During fiscal 2015 the Company recorded $1.7 million of restructuring costs, largely related to the Company's consolidation of its manufacturing facilities in Wisconsin, as well as its relocation of manufacturing operations from Juarez, Mexico to Guadalajara, Mexico. (5) The Company defines return on invested capital ("ROIC"), a non-GAAP financial measure, as tax-effected operating income divided by average invested capital over a rolling five-quarter period. Invested capital is defined as equity plus debt, less cash and cash equivalents, as discussed in Part II, Item 7, "Management’s Discussion and Analysis of Financial Condition and Results of Operations - Return on Invested Capital ("ROIC") and Economic Return." For a reconciliation of ROIC and Economic Return to our financial statements that were prepared in accordance with GAAP, see Exhibit 99.1 to this annual report on Form 10-K. (6) Fiscal 2015 included 53 weeks. All other periods presented included 52 weeks.
table: Fiscal Years Ended
table: Income Statement Data  September 28,
  2019 September 29,
  2018 September 30,
  2017 October 1,
  2016 October 3,
  2015(6)
table: Net sales $3,164,434 $2,873,508 $2,528,052 $2,556,004 $2,654,290
table: Gross profit 291,838 257,600 255,855 227,359 239,550
table: Gross margin percentage 9.2% 9.0% 10.1% 8.9% 9.0%
table: Operating income (2) (3) (4) 142,055 118,283 129,908 99,439 115,436
table: Operating margin percentage (2) (3) (4) 4.5% 4.1% 5.1% 3.9% 4.3%
table: Net income (1) (2) (3) (4) 108,616 13,040 112,062 76,427 94,332
table: Earnings per share (diluted) (1) (2) (3) (4) $3.50 $0.38 $3.24 $2.24 $2.74
table: Cash Flow Statement Data
table: Cash flows provided by operations $115,300 $66,831 $171,734 $127,738 $76,572
table: Capital equipment additions 90,600 62,780 38,538 31,123 35,076
table: Balance Sheet Data
table: Total assets $2,000,883 $1,932,642 $1,976,182 $1,765,819 $1,691,760
table: Total debt obligations 287,980 188,617 313,107 262,509 261,806
table: Shareholders’ equity 865,576 921,143 1,025,939 916,797 842,272
table: Return on invested capital (5) 13.1% 16.1% 16.2% 13.8% 14.0%
table: Inventory turnover ratio 3.8x  3.6x  3.7x  4.2x  4.3x
question: Analyse this data from a financial earnings document. What was the change in the gross profit between 2015 and 2016?