A reconciliation of the statutory federal income tax rate to our effective rate for continuing operations is provided below:

	Three Months Ended March 31,
	2019			2018
Statutory federal income tax rate		21.0	%		21.0	%
State income taxes, net of federal income tax		4.2			5.0
Stock compensation windfall benefit		(0.1	)		(16.5	)
Permanent differences and other		(1.1	)		(0.9	)
		24.0	%		8.6	%

We base our estimate of deferred tax assets and liabilities on current tax laws and rates. In certain cases, we also base our estimate on business plan forecasts and other expectations about future outcomes. Changes in existing tax laws or rates could affect our actual tax results, and future business results may affect the amount of our deferred tax liabilities or the valuation of our deferred tax assets over time. Due to uncertainties in the estimation process, particularly with respect to changes in facts and circumstances in future reporting periods, as well as the residential homebuilding industry’s cyclicality and sensitivity to changes in economic conditions, it is possible that actual results could differ from the estimates used in previous analyses.

Accounting for deferred taxes is based upon estimates of future results. Differences between the anticipated and actual outcomes of these future results could have a material impact on our consolidated results of operations or financial position.