An additional consideration in thinking about optimal currency areas

Traditionally, when we think about currency pegging, we think that if two countries are exposed to highly correlated shocks, then pegging is not a bad idea. E.g. if Austria and Germany have the same business cycle, it is not a bad idea for Austria to adopt German monetary policy. By this logic, it is a bad idea for Qatar to adopt US monetary policy. Now suppose there are two countries which have common shocks but dissimilar per capita income and thus different CPI consumption baskets. This lead