and option contracts amount should not be in excess of specifically identified anticipated transactions. By their very nature, our estimates of anticipated transactions may fluctuate over time and may ultimately vary from actual transactions. When anticipated transaction estimates or actual transaction amounts decline below hedged levels, or if it is no longer probable that a forecasted transaction will occur by the end of the originally specified time period or within an additional two-month period of time thereafter, we are required to reclassify the cumulative changes in fair values of the over-hedged portion of the related hedge contract from other comprehensive income to other expense (income), net during the quarter in which such changes occur. 

We use forward contracts to hedge our investment in the net assets of certain international subsidiaries to offset foreign currency translation related to our net investment in those subsidiaries. The change in fair value of the forward contracts hedging our net investments is reported in the cumulative translation adjustment component of accumulated other comprehensive income within stockholders’ equity, to the extent effective, to offset the foreign currency translation adjustments on those investments. As the value of our underlying net investments in wholly-owned international subsidiaries is known at the time a hedge is placed, the designated hedge is matched to the portion of our net investment at risk. Accordingly, the variability involved in net investment hedges is substantially less than that of other types of hedge transactions and we do not expect any material ineffectiveness. We consider, on a quarterly basis, the need to redesignate existing hedge relationships based on changes in the underlying net investment. Should the level of our net investment decrease below hedged levels, the cumulative change in fair value of the over-hedged portion of the related hedge contract would be reported directly to earnings in the period in which changes occur. 

Stock-based Compensation 

We account for stock-based compensation by estimating the fair value of stock-based compensation on the date of grant using the Black-Scholes option pricing model. The Black-Scholes option pricing model requires the input of highly subjective assumptions including volatility. Expected volatility is estimated based on implied volatility in market traded options on our common stock with a term greater than one year, along with other factors. Our decision to use implied volatility was based on the availability of actively traded options on our common stock and our assessment that implied volatility is more representative of future stock price trends than historical volatility. If factors change and we use different assumptions for estimating stock-based compensation expense in future periods, stock-based compensation expense may differ materially in the future from that recorded in the current period. 

Taxes 

We record valuation allowances against our deferred tax assets, when necessary. Realization of deferred tax assets (such as net operating loss carry-forwards) is dependent on future taxable earnings and is