Income Taxes	9 Months Ended
Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Note 8 — Income Taxes Forrester provides for income taxes on an interim basis according to management’s estimate of the effective tax rate expected to be applicable for the full fiscal year. Certain items such as changes in tax rates and tax benefits related to disqualifying dispositions of incentive stock options are treated as discrete items and are recorded in the period in which they arise. Income tax expense for the nine months ended September 30, 2016 was $9.1 million resulting in an effective tax rate of 43.4% for the period. Income tax expense for the nine months ended September 30, 2015 was $5.3 million resulting in an effective tax rate of 34.8% for the period. The increase in the effective tax rate for the nine months ended September 30, 2016 compared to the prior year period was primarily due to the 2016 period including $0.6 million of tax expense due to a valuation allowance on a capital loss generated from one of the Company’s investments. In addition, in 2015 the Company realized a tax benefit of $0.7 million related to the 2015 ruling of the United States Tax Court in Altera Corp. et al. v. Commissioner which invalidated the 2003 final Treasury rule that had required participants in qualified cost-sharing arrangements to share stock-based compensation costs.

Income Taxes

9 Months Ended

Sep. 30, 2016

Note 8 — Income Taxes

Forrester provides for income taxes on an interim basis according to management’s estimate of the effective tax rate expected to be applicable for the full fiscal year. Certain items such as changes in tax rates and tax benefits related to disqualifying dispositions of incentive stock options are treated as discrete items and are recorded in the period in which they arise.

Income tax expense for the nine months ended September 30, 2016 was $9.1 million resulting in an effective tax rate of 43.4% for the period. Income tax expense for the nine months ended September 30, 2015 was $5.3 million resulting in an effective tax rate of 34.8% for the period. The increase in the effective tax rate for the nine months ended September 30, 2016 compared to the prior year period was primarily due to the 2016 period including $0.6 million of tax expense due to a valuation allowance on a capital loss generated from one of the Company’s investments. In addition, in 2015 the Company realized a tax benefit of $0.7 million related to the 2015 ruling of the United States Tax Court in Altera Corp. et al. v. Commissioner which invalidated the 2003 final Treasury rule that had required participants in qualified cost-sharing arrangements to share stock-based compensation costs.