GAAP operating expenses for first quarter 2019 were $70.3 million, or 23.3 percent of revenue, and $65.8 million, or 21.8 percent of revenue, on a non-GAAP basis, which excluded $4.5 million of amortization of acquisition-related intangible asset expenses. GAAP operating expenses in the first quarter 2018 were $71.7 million, or 26.1 percent of revenue, and in the fourth quarter 2018 were $70.3 million, or 22.4 percent of revenue.
First quarter 2019 GAAP net income was a record $31.7 million, or $0.62 per diluted share, compared to GAAP net income of $18.5 million, or $0.37 per share, in first quarter 2018 and GAAP net income of $29.5 million, or $0.58 per diluted share, in fourth quarter 2018.
First quarter 2019 non-GAAP adjusted net income was a record $35.4 million, or $0.69 per diluted share, which excluded, net of tax, $3.7 million of non-cash acquisition-related intangible asset amortization costs. This compares to non-GAAP adjusted net income of $24.2 million, or $0.48 per diluted share, in the first quarter 2018 and $33.2 million, or $0.65 per diluted share, in the fourth quarter 2018.
The following is an unaudited summary reconciliation of GAAP net income to non-GAAP adjusted net income and per share data, net of tax (in thousands, except per share data):
| Three Months Ended | |||||
| March 31, 2019 | |||||
| GAAP net income | $ | 31,716 | |||
| GAAP diluted earnings per share | $ | 0.62 | |||
| Adjustments to reconcile net income to non-GAAP net income: | |||||
| Amortization of acquisition-related intangible assets | 3,674 | ||||
| Non-GAAP net income | $ | 35,390 | |||
| Non-GAAP diluted earnings per share | $ | 0.69 | |||
| Note: Throughout this release, we refer to “net income attributable to common stockholders” as “net income.” |
