Bell \& Howell Company's 1986 annual report to its stockholders included financial statements for the year ended December 31, 1986. Those statements showed that Bell \& Howell had earned a \(\$ 32,895,000\) net income in 1986 . The footnotes to the 1986 financial statements contained the following item:

\section*{Note A}

\section*{Significant Accounting Policies:}

Property and Depreciation. Property, plant, and equipment is recorded at cost. In general, the straightline method of depreciation is used for asset additions since the beginning of 1981 and the double-decliningbalance method is used for prior years' assets.

Estimated lives range from 5 to 35 years for land improvements, 10 to 50 years for buildings, 2 to 15 years for machinery and equipment, and 5 to 15 years for product masters.

Courlesy of Bell \& Howell Company.

Why might Bell \& Howell have chosen to switch from declining-balance depreciation to straight-line depreciation for assets purchased in 1981 and subsequent years? Assuming that the company's total investments in property, plant, and equipment have increased gradually each year, what effect would this change have on comparisons of income earned before and after 1980?