Until just a few years ago, goodwill was amortized over time. Starting in December 2001, the accounting changed so that goodwill stays on the books for the original amount unless the fair value of ...
Ramanna, Karthik, and Ross L. Watts. "Evidence on the Use of Unverifiable Estimates in Required Goodwill Impairment." Review of Accounting Studies 17, no. 4 (December 2012): 749–780.