But both academic research and anecdotal evidence bear out time and again the hesitancy of managers to apply NPV in the manner they have been taught. For example, in a 1987 study, Harvard economist Lawrence Summers found that companies were using hurdle rates ranging from 8% to 30%, with a median of 15% and a mean of 17%. Allowing for the deductibility of interest expenses, the nominal interest rate during the period in question was only 4%, and the real rate was close to zero. Although the hurdle rate appropriate for investment with a nondiversifiable risk usually exceeds the riskless rate, it is not enough to justify the large discrepancies found. More recent studies have confirmed that managers regularly and consciously set hurdle rates that are often three or four times their weighted average cost of capital