Before getting on to that, however, it’s necessary to delve into the weeds of bond maths, and outline some definitions.
As noted above, duration is a mathematical concept that refers to the sensitivity of an asset – typically a bond – to changes in interest rates; the higher the duration, the more sensitive an asset is to shifts in rates, and vice versa. Bond duration is relatively easy to measure, as fixed income products pay a regular amount, on a fixed schedule, for the life of the instrument. In contrast, equities do not necessarily pay a regular amount on a regular timescale, with said payments instead being constructed as dividends, which are paid subject to a company’s performance and financial situation at a given time. With this in mind, one could consider equity duration as a measure of how long an investor must receive dividends in order to be repaid the purchase price of the stock. It is that irregularity of cash flows that makes equity duration difficult to measure and means that, at best, it is only possible to approximate a value for such a concept.
With all of that said and done, there are ways that one is able to gauge the relationship between equities and fixed income. At a, perhaps, crude level, a simple overlay chart helps to paint a picture – as shown below, the inverse relationship (2s are on an inverted Y-axis here) between front-end rates and the Nasdaq 100 has broken down since the end of January.