Table:
|  | Years ended December 31, |  |  |  |
| --- | --- | --- | --- | --- |
|  | 2019 | 2018 | $ Difference | % Difference |
| Selling, general and administrative expense | $24,371,349 | $14,794,205 | $9,577,144 | 64.7% |
| Research, development and engineering expense | 7,496,012 | 3,766,160 | 3,729,852 | 99.0% |
| Total operating expense | $31,867,361 | $18,560,365 | $13,306,996 | 71.7% |
Paragraphs:
Operating Expense
Selling, general and administrative expense increased $9.6 million to $24.4 million for the year ended December 31, 2019 compared to $14.8 million for the year ended December 31, 2018. Selling, general and administrative expense increased primarily due to $4.4 million of expenses associated with the legacy business of MOI and $2.0 million of expenses associated with the legacy business of GP , in addition to $1.0 million in transaction costs associated with the acquisition of GP, a $0.9 million increase in share-based compensation as a result of new awards, and a $1.1 million increase in expenses related to sales and marketing as a result of increased revenue.
Research, development and engineering expenses increased $3.7 million to $7.5 million for the year ended December 31, 2019 compared to $3.8 million for the year ended December 31, 2018 primarily due to $1.1 million of research, development and engineering expense associated with the legacy business of MOI and $2.7 million of research, development and engineering expense associated with the legacy business of GP during the year ended December 31, 2019.
Question:
In which year was Selling, general and administrative expense less than 20,000,000?
Answer: Because locate and analyze Selling, general and administrative expense in row 3, the answer is: 2018.