The study looked at long-term interest rates and found that for maturities longer than 20 years, there is a downward slope that can't be explained by normal factors. They also discovered that volatility at the very long end of the yield curve is higher than expected. By creating a model-based extrapolation of the yield curve, they found that the regulatory discount curve is too smooth and doesn't account for the actual behavior of long-term rates. This means that the mean-reversion and smoothing in the regulatory curve are too strong.