In all pericyclic reactions I have observed, I have noticed that the number of existing pi bonds must equal the number of formed sigma bonds and vice versa. This is normal for bond changing in electrocyclic, clycloaddition, group transfer reactions and cheletropic reactions. The classes of pericyclic reactions seen at http://en.wikipedia.org/wiki/Pericyclic_reaction with list of bond changing from sigma to pi and as I have observed, bond can be conserved regardless of which bond is being broken of formed. However, sigmatropic and dyotropic reactions, sigma and pi bonds remain unchanged and still maintain bond conservation. As it is for orbital symmetry and conservation, bond conservation could be an interesting phenomena in pericyclic reactions.