Goodwill represents the excess of the purchase price over the estimated fair value of the net tangible and identifiable intangible assets acquired in business combinations.  Our annual impairment assessment of our single reporting unit is performed as of the fourth quarter of each year, and an assessment is performed at other times if an event occurs or circumstances change that would more likely than not reduce the fair value of the asset below its carrying value.  If the carrying value of goodwill exceeds its fair value, an impairment loss is recognized.

As of September 30, 2015, there were no indicators of impairment and no impairment loss was recorded for goodwill during the three and nine months ended September 30, 2015 and 2014.  As of September 30, 2015, the cumulative balance of goodwill impairments recorded since the July 2008 merger (the "Merger") between our wholly owned subsidiary, Vernon Merger Corporation, and XM Satellite Radio Holdings Inc. ("XM"), was $4,766,190, which was recognized during the year ended December 31, 2008.