Which of the following statements regarding book-tax differences associated with purchased goodwill is false?

1. It is possible to have no book-tax difference in a year when there is no goodwill amortization for tax purposes.

2. In a year when goodwill is impaired and yet fully amortized for tax purposes (so no tax amortization of the goodwill for that year), the book-tax difference will be unfavorable.

3. Temporary book-tax differences associated with goodwill are always favorable.

4. If goodwill has been fully amortized for tax purposes in a previous year, the book-tax difference is equal to the amount of impairment recognized.