Table:
| ($ in million) |  |  |  |
| --- | --- | --- | --- |
| For the year ended December 31: | 2019 | 2018 | Yr.-to-Yr. Percent Change |
| Total consolidated research, development and engineering | $5,989 | $5,379 | 11.3% |
| Non-operating adjustment |  |  |  |
| Acquisition-related charges | (53) | - | NM |
| Operating (non-GAAP) research, development and engineering | $5,936 | $5,379 | 10.4% |
Paragraphs:
Research, Development and Engineering Expense
NM—Not meaningful
Research, development and engineering (RD&E) expense was 7.8 percent of revenue in 2019 and 6.8 percent of revenue in 2018.
RD&E expense increased 11.3 percent in 2019 versus 2018 primarily driven by: • Higher spending (11 points) including investment in the z15 and Red Hat spending in the second half of 2019 (8 points); and • Higher acquisition-related charges associated with the Red Hat transaction (1 point); partially offset by • The effects of currency (1 point).
Operating (non-GAAP) expense increased 10.4 percent year to year primarily driven by the same factors excluding the acquisition-related charges associated with the Red Hat transaction.
Question:
What caused the Operating (non-GAAP) expense increase?
Answer: Operating (non-GAAP) expense increased 10.4 percent year to year primarily driven by the same factors excluding the acquisition-related charges associated with the Red Hat transaction.