The calculations of basic and diluted net income per share for the three months ended March 31, 2015 and 2014 are as follows (dollars in thousands, except for per share data): | | | | | | | | | | Three Months Ended
March 31, | | 2015 | | 2014 | Basic: | | | | Net income attributable to common stockholders | $ | 6,410 |
| | $ | 10,274 |
| Weighted average number of common shares outstanding | 17,302,522 |
| | 17,054,598 |
| Basic net income per share attributable to common stockholders | $ | 0.37 |
| | $ | 0.60 |
| Diluted: | | | | Net income attributable to common stockholders | $ | 6,410 |
| | $ | 10,274 |
| Weighted average number of common shares outstanding | 17,302,522 |
| | 17,054,598 |
| Weighted average number of dilutive common share equivalents from options to purchase common stock | 412,891 |
| | 512,985 |
| Common shares and common share equivalents | 17,715,413 |
| | 17,567,583 |
| Diluted net income per share | $ | 0.36 |
| | $ | 0.58 |
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