Changes in the carrying amount of goodwill were as follows:

During the fourth quarter of 2017, we experienced poor performance of our common stock, which led management to believe that a triggering event occurred. As such, an updated goodwill impairment test was performed. The result of the impairment test indicated that the carrying value of goodwill was above the implied fair value.

For the purposes of the goodwill impairment test, we estimated the fair value of our sole reporting unit using the market approach. Under the market approach, we utilized the market capitalization of our common stock, and applied an estimated control premium based on an analysis of control premiums paid in acquisitions of companies in the same or similar industries. Because the significant inputs used in this analysis are readily available from public markets or can be derived from observable market transactions, they have been classified as level 2 in the fair value hierarchy. Based on this approach, we determined that the carrying value of our sole reporting unit exceeded the fair value by $10.7 million, which was recorded in “Impairment of goodwill” in the Consolidated Statement of Operations for the year ended December 31, 2017.