S•1/A Table of Contrail savings method, or cost savings method, all of which are a form of a discounted cash flow analysis. An impairment charge of a reporting unit's goodwill could have a material adverse effect on our financial results. An impairment charge may be caused by changes in the underlying business and economic conditions, the most relevant of which would be a deterioration in global economic conditions. Deterioration in global economic conditions could cause us to experience a decrease in our Adjusted EBITDA. Furthermore, volatility in the debt markets which impacted our debt yields, could affect these estimates used in the analysis discussed above, which in turn could affect the fair value of the repotting unit. Thus, it is possible for reporting units that record impairments to record additional impairments in the future. All key assumptions and valuations are determined by and arc the responsibility of management. The factors used in the impairment analysis are inherently subject to uncertainty. We believe that we have made reasonable estimates and assumptions to determine the fair value of our reporting units, if actual results are not consistent with these estimates and assumptions, goodwill and other intangible assets may be overstated which could trigger an impairment charge. As of December 31, 2014. the carrying value of goodwill was $17.0 billion, of which $14.3 billion was related to our GBS reporting unit. As of June 30, 2015, the most recent impairment analysis date, the fair value of our reporting units substantially exceeded their carrying value with the exception of our GBS reporting unit. Our GBS reporting unit's carrying value exceeded fair value by 17%. Examples of events or circumstances that could reasonably be expected to negatively affect the underlying key assumptions and ultimately impact the estimated fair value of the aforementioned GBS reporting unit may include such items as the following: Global economic, pol