Table:
|  |  | Fiscal Years Ended March 31, |  |
| --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 |
| Net sales (1) | $1,382,818 | $1,200,181 | $757,338 |
| Cost of sales (1) | 924,276 | 860,744 | 571,944 |
| Gross Margin (GAAP) (1) | 458,542 | 339,437 | 185,394 |
| Gross margin as a % of net sales | 33.2% | 28.3% | 24.5% |
| Non-GAAP adjustments: |  |  |  |
| Plant start-up costs (2) | (927) | 929 | 427 |
| Stock-based compensation expense | 2,756 | 1,519 | 1,384 |
| Adjusted gross margin (non-GAAP) (1) | $460,371 | $341,885 | $187,205 |
| Adjusted gross margin as a % of net sales | 33.3% | 28.5% | 24.7% |
Paragraphs:
Non-GAAP Financial Measures
To complement our Consolidated Statements of Operations and Cash Flows, we use non-GAAP financial measures of Adjusted gross margin, Adjusted operating income, Adjusted net income, and Adjusted EBITDA. We believe that Adjusted gross margin, Adjusted operating income, Adjusted net income, and Adjusted EBITDA are complements to U.S. GAAP amounts and such measures are useful to investors. The presentation of these non-GAAP measures is not meant to be considered in isolation or as an alternative to net income as an indicator of our performance, or as an alternative to cash flows from operating activities as a measure of liquidity.
The following table provides a reconciliation from U.S. GAAP Gross margin to non-GAAP Adjusted gross margin (amounts in thousands):
(1) Fiscal years ending March 31, 2018 and 2017 adjusted due to the adoption of ASC 606.
(2) $0.9 million in costs incurred during fiscal year 2018 related to the relocation of the Company's tantalum powder facility equipment from Carson City, Nevada to its existing Matamoros, Mexico plant were reclassified from “Plant start-up costs” to “Restructuring charges” during fiscal year 2019.
Question:
What was the percentage change in Stock-based compensation expense between 2018 and 2019?
Answer: (2756-1519)/1519 = 81.44