The yield gap or yield ratio is the ratio of the dividend yield of an equity and the yield of a long-term government bond. Typically equities have a higher yield (as a percentage of the market price of the equity thus reflecting the higher risk of holding an equity.
The purpose of calculating the yield gap is to assess whether the equity is over or under priced as compared to bonds. For a given equity, the following cases may be considered:
References
Yield gap Wikipedia(Text) CC BY-SA