What is the logic behind using just one cost of debt financing rather

What is the logic behind using just one cost of debt financing rather than estimating the cost of financing with each specific issue of long and short-term debt?

What will be an ideal response?

ANSWER

The logic behind using just one rate–a long-term yield–for both short-term and long-term debt is that while short-term yields may differ from long-term yields (usually lower), over a long period, short-term rates on average tend to be similar to long-term rates. This logic is consistent with the “unbiased expectations theory”