Frozen-rate duration

The Macaulay duration of a perpetual preferred if its dividend rate never changes: (1 + i) ÷ (m × i), with i the effective yield per period and m payments a year. At a 10% yield paid monthly it is about 10.1 years.

It measures price sensitivity to yield for fixed-rate perpetuals such as STRF, STRK and STRD. It overstates the sensitivity of a variable-rate preferred, whose rate resets.