Discuss the pros and cons of using different potential raters to appraise a persons performance

Suppose interest rates on residential mortgages of equal risk are 5.5% in california and 7.0% in new york. could this differential persist? what forces might tend to equalize rates? would differentials in borrowing costs for businesses of equal risk located in california and new york be more or less likely to exist than differentials in residential mortgage rates? would differentials in the cost of money for new york and california firms be more likely to exist if the firms being compared were very large or if they were very small? what are the implications of all of this with respect to nationwide branching?