Basic earnings per share is computed using the weighted average number of common shares outstanding during the period, and diluted earnings per share is computed using the weighted average number of common shares outstanding during the period adjusted for all potentially dilutive common stock equivalents, except in cases where the effect of the common stock equivalent would be antidilutive. The amounts used to compute the basic and diluted earnings per share for the three and six months ended June 30, 2011 and 2010 are illustrated below (in thousands):

 

 

For the three and six months ended June 30, 2011 and 2010, a nominal amount of stock options were excluded from the computation of diluted earnings per share because the exercise prices of these common stock equivalents were greater than the average market price of Quanta’s common stock. The 3.9 million exchangeable shares of a Canadian subsidiary of Quanta that were issued pursuant to the acquisition of Valard on October 25, 2010, which are exchangeable on a one-for-one basis with Quanta common shares, are included in weighted average shares outstanding for basic and diluted earnings per share for the three and six months ended June 30, 2011. Shares placed in escrow related to the acquisition of Price Gregory are included in the computation of diluted earnings per share for all periods based on the portion of the period they were in escrow. These shares were released from escrow on April 4, 2011. For the three and six months ended June 30, 2010, the effect of assuming conversion of Quanta’s 3.75% convertible subordinated notes due 2026 (3.75% Notes) would have been antidilutive and therefore the shares issuable upon conversion were excluded from the calculation of diluted earnings per share. The 3.75% Notes were not outstanding after May 14, 2010 and therefore had no impact on diluted shares during the three and six months ended June 30, 2011.