The interest cost of split-rated municipal bonds before and after Moody's recalibration in 2010

Purpose - In April and May of 2010 Moody's recalibrated its municipal bond ratings to a global scale, the system they use for other asset classes and the same scale used by Standard and Poor's (S&P). The authors investigate the impact of Moody's recalibration on true interest cost (TIC) of competitively-sold, uninsured, new bond issues with split bond ratings, by looking at a sample of bond issues before recalibration (1997–2010) and after recalibration (2010–2017). Design/methodology/approach - Two different hypotheses are tested for each period to estimate whether TIC remains the same when the S&P rating is higher (H1) than Moody's rating or lower (H2) compared to bond issues for which the S&P and Moody's rating are the same. Further, two additional hypotheses are tested. H3 tests whether the impact of having a higher rating from S&P is the same as having a lower rating from S&P. H4 tests whether the impact of having a split rating is the same in the pre- and post-recalibration period. Findings - Tests suggest that before recalibration a higher S&P rating leads to significantly lower interest costs, but a lower S&P rating does not lead to significantly higher costs. After recalibration, a higher S&P rating leads to significantly lower interest costs; however, a lower S&P rating leads to significantly higher interest costs for the bonds in the sample. The findings also suggest that the rating systems of Moody's and S&P became more similar to each other after recalibration and that the impact on interest cost of a higher S&P rating is reduced after the recalibration. Originality/value - It appears that a given Moody's rating (which used higher credit standards in the period before recalibration) was more influential than the S&P rating prior to recalibration because investors “ignored” a lower S&P rating during this period. After recalibration, the lower S&P rating was no longer ignored by investors. Therefore, Moody's recalibration seems to have had the intended effect of moving the credit standards of the two rating agencies more into parity. This provides value to investors since they may now assume, unlike the situation in the pre-recalibration period, that similar ratings from the two companies provide similar information about the probability of default and loss that would occur following a default. From the standpoint of regulators, the municipal credit information is easier to understand and is more transparent for investors.