Table:
|  | 2019 | As a % of Segment Revenue (1) | 2018 | As a % of Segment Revenue (1) |
| --- | --- | --- | --- | --- |
| PSG | $976.0 | 35.0 % | $ 1,110.1 | 36.5 % |
| ASG | 794.8 | 40.3 % | 878.3 | 42.4 % |
| ISG | 275.4 | 36.4 % | 317.1 | 41.2 % |
| Gross profit for all segments | $ 2,046.2 |  | $ 2,305.5 |  |
| Unallocated manufacturing costs (2) | (72.6) | (1.3) % | (66.8) | (1.1) % |
| Total gross profit | $ 1,973.6 | 35.8 % | $ 2,238.7 | 38.1 % |
Paragraphs:
Gross Profit and Gross Margin (exclusive of amortization of acquisition-related intangible assets described below)
Our gross profit by reportable segment was as follows (dollars in millions):
(1) Certain of the amounts may not total due to rounding of individual amounts. (2) Unallocated manufacturing costs are presented as a percentage of total revenue (includes expensing of the fair market value step-up of inventory of $19.6 million during 2019 and $1.0 million during 2018).
The decrease in gross profit of $265.1 million, or approximately 12%, was primarily due to the impact of the decrease in sales volume, higher fixed costs due to the expansion in our manufacturing capacity as well as the expensing of $19.6 million excess over book value of inventory, commonly referred to as the fair market value step-up, from the Quantenna acquisition.
Gross margin decreased to 35.8% during 2019 compared to 38.1% during 2018. The decrease was due to a competitive pricing environment resulting in a decline in average selling prices, higher demand for lower margin products, increased manufacturing costs due to a higher mix of external manufacturing and decreased demand for our products, as explained in the revenue section.
Question:
How much was the expensing of the fair market value step-up of inventory during 2019?
Answer: $19.6 million