FASB Actions
Back in 2001, FASB (the Financial Accounting Standards Board) abolished the amortization of goodwill, which led to an increase in a given company’s EPS, a factor that boosted the average share prices but only for a short time. Investors soon realized that amortization doesn’t really affect the cash flows or operations, and thus things returned to normal. Of course, a few companies' share prices dropped on the news. In early 2014, FASB announced new alternative rules for private companies according to which goodwill will be amortized and also tested for impairment when the need arises. The effect of amortization changes in goodwill on share prices is usually temporary and not severe.
The outcome of impairment loss and write-downs on share prices depends on whether the market has already factored in the likelihood of such an event based on any management disclosures. In January 2002, Time Warner (NYSE: TWX) announced a massive $54 billion write-off in goodwill. The stock price was slightly higher on the day of announcement, as the market had already anticipated such an event. But the company's stock had corrected by 37% of its value over the six-month period preceding the announcement. This proves that investors did not take the news positively. However, the response was spread over a time period and was triggered when such news was brewing.
Interestingly, this process also works the other way around, where stock price declines can trigger the need for an impairment test of goodwill. This is mainly because in goodwill testing for impairment, market capitalization of the company is relevant and decreases with a fall in share prices.