The computation of basic and diluted net loss per share for the periods indicated is as follows:

At December 31, 2017, 2016 and 2015, we were contingently obligated to pay $0.1 million, $0.8 million and $0.5 million, which may be settled, at our option, in either cash or an equivalent amount of common shares based upon their then-current market value, if certain performance criteria had been met. The equivalent amount of common shares have been excluded from the computation of diluted net loss per share for the years ended December 31, 2017, 2016 and 2015, as they were antidilutive.

Included in the computation of basic net loss per share for the years ended December 31, 2016 and 2015 were 53,335 and 292,967 potentially dilutive shares, respectively, representing $0.6 million and $6.5 million, respectively, of the total contingent obligation related to shares we unconditionally agreed to issue.

At December 31, 2017, 2016 and 2015, 24,875, 27,828 and 31,483 outstanding options, respectively, with an average exercise price of $44.45, $44.76 and $43.64, respectively, were not recognized in the diluted earnings per share calculation as they were antidilutive.