Table:
| ($ in millions) |  |  |  |
| --- | --- | --- | --- |
| For the year ended December 31: | 2019 | 2018 | Yr.-to-Yr Percent/ Margin Change |
| Systems |  |  |  |
| External Systems Hardware gross profit | $2,622 | $2,590 | 1.2% |
| External Systems Hardware gross profit margin | 44.3% | 40.7% | 3.6pts. |
| External Operating Systems Software gross profit | $1,412 | $1,412 | 0.0% |
| External Operating Systems Software gross profit margin | 83.8% | 84.5% | (0.7)pts. |
| External total gross profit | $4,034 | $4,002 | 0.8% |
| External total gross profit margin | 53.1% | 49.8% | 3.2pts. |
| Pre-tax income | $701 | $904 | (22.4)% |
| Pre-tax margin | 8.4% | 10.2% | (1.8)pts. |
Paragraphs:
The Systems gross profit margin increased 3.2 points to 53.1 percent in 2019 compared to the prior year. The increase was driven by actions taken in 2018 to better position the cost structure over the longer term, a mix to IBM Z hardware and operating systems and margin improvement in Storage Systems.
Pre-tax income of $701 million declined 22.4 percent and pre-tax margin of 8.4 percent decreased 1.8 points year to year driven by the declines in Power Systems and Storage Systems revenue and the continued investment in innovation across the Systems portfolio, mitigated by the benefit from the new hardware launches in the second-half 2019.
Question:
What caused the increase in the Systems gross profit margin?
Answer: The increase was driven by actions taken in 2018 to better position the cost structure over the longer term, a mix to IBM Z hardware and operating systems and margin improvement in Storage Systems.