Table:
|  |  | For the Fiscal Years Ended |  |  |
| --- | --- | --- | --- | --- |
|  | March 31, 2019 |  | March 31, 2018 |  |
| Sales | Amount | % to Net Sales | Amount | % to Net Sales |
| Net sales | $240,740 |  | $226,964 |  |
| Segment operating income | 22,546 | 9.4% | 15,694 | 6.9% |
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Electro-Magnetic, Sensors, and Actuators
The following table sets forth net sales, operating income, and operating income as a percentage of net sales for our MSA reportable segment in fiscal years 2019 and 2018 (amounts in thousands, except percentages).
Net Sales MSA net sales of $240.7 million in fiscal year 2019 increased $13.8 million or 6.1% from $227.0 million in fiscal year 2018. The increase in net sales was primarily driven by a $15.0 million increase in OEM sales in the JPKO region. Also contributing to the increase in net sales was a $4.3 million increase in EMS sales across all regions and a $3.7 million increase in distributor sales across the Americas and EMEA regions. These increase in net sales were partially offset by a $5.5 million decrease in distributor sales across the APAC and JPKO regions and a $3.8 million decrease in OEM sales across the Americas, APAC, and JPKO regions.
Reportable Segment Operating Income
Segment operating income of $22.5 million in fiscal year 2019 increased $6.9 million from $15.7 million in fiscal year 2018. The increase in operating income was primarily due to a $6.6 million decrease in SG&A expenses resulting from a decrease in payroll expenses that was caused by a reduction in head count. Also contributing to the increase in operating income was a $2.9 million decrease in restructuring charges, a $1.3 million decrease in net loss on write down and disposal of long-lived assets, and a $0.2 million decrease in R&D expenses. Partially offsetting these improvements was a $4.1 million decrease in gross margin, which was primarily driven by a change in the sales mix to lower margin products.
Question:
What was the main driver of MSA net sales increase between 2018 and 2019?
Answer: primarily driven by a $15.0 million increase in OEM sales in the JPKO region.