Lev and Nissim (2004) focus on how the magnitude of the book-tax differences affects earnings growth. They posit that the ratio of estimated taxable income to book income (TI/BI) is a measure of earnings quality (and thus contains information incremental to that found in accruals and cash flows) for three reasons. First, discretionary accruals are included in book income but often are excluded from taxable income, and since discretionary accruals must reverse in the future, they reduce earnings quality. Second, if firms time transactions to smooth taxable income, then estimated current-period taxable income should reflect management’s assessment of future taxable income.