• Bonds trading near or below par are much more sensitive to interest rates than reported by standard analytics systems
  • Investors who rely on these systems will be in for an unpleasant surprise when rates rise
  • Kalotay Analytics and Investortools, Inc. have partnered to do things right.

During recent years of historically low interest rates, with most municipal bonds trading at a premium, investors have paid little attention to the adverse effect of taxes on the prices of discount bonds. As a result, investors have neither seriously challenged, nor required Currently Used Platforms (CUPs) to provide correct interest rate risk measures for bonds trading near or below par. The reality is that CUPs grossly underestimate the effect of rising rates.

Although interest is tax-exempt, the gain resulting from purchasing a muni at a deep discount – below the so-called de minimis threshold – is subject to severe tax treatment. It is taxed as ordinary income at maturity at a rate of about 40% for the typical investor. Thus, purchasing a bond at 80 would trigger an 8-point tax liability and cost the investor 3.2% of par at maturity.

We analyzed a portfolio of 185 munis which currently trade near par (blue in the graph below). After shocking interest rates up by 100 basis points, predictably the prices fall below par. However, as calculated by CUPs, the prices (red) don’t fall far enough. They are hugely overestimated, by over 3 points in many cases. The source of the problem is that CUPs disregard the tax payable on the discount at maturity, which depresses the prices further, as correctly calculated by MuniOAS™ (green).



Let’s review the results for Bond #1 (Tempe, AZ) in the table below. The current price of this bond is 99.20. The corresponding pre-tax and after-tax YTM’s are 3.080% and 3.069% respectively. The after-tax YTM is lower due to the tax at maturity on the 0.80 point gain. According to the CUPs, a 100 bps increase of the yield curve would reduce the price to 89.33 (pretax YTM 4.127%). However, the corresponding after-tax YTM would be 3.828%, which is only 76 bps higher than the original YTM – recall that the rates were assumed to have increased by 100 bps.

In contrast, according to MuniOAS™ the price would decline to 86.10 (pretax YTM 4.499%, after-tax YTM 4.108%). Thus according to MuniOAS the after-tax yield would increase by 104 bps, roughly as expected. As indicated in the table, the difference between the CUPs price and the MuniOAS price is 89.33-86.10=3.21 points. In other words, CUPs are reporting materially misleading results when calculating the effect of rising rates on discount munis.


Investortools has partially implemented MuniOAS™ features and expects to make true tax-affected duration and OAS available in Perform by the Q3 2015.

About Kalotay Analytics

Incorporating taxes is vital to the correct analysis of municipal bonds, because the prices of discount munis are depressed by the tax payable at maturity by the buyer. Investortools has partnered with Andrew Kalotay Associates, the developer of patent-pending tax-integrated analytics for munis, in order to bring this essential technology to our clients. Applications include rich/cheap analysis, risk management, and tax management.

This Tax-Aware Resource Center will keep you abreast of related articles and presentations.