In 1991, he received a PhD for his thesis titled "Essays on Banking" under the supervision of Stewart Myers, consisting of three essays on the nature of the relationship between a firm or a country, and its creditor banks. The nature of financial systems had witnessed widespread changes in the 1980s, with markets getting deregulated, information becoming more widely available and easier to process, and competition having increased. The established orthodoxy claimed that deregulation must necessarily increase competition, which would translate into greater efficiency. In his thesis, Rajan argued that this might not necessarily be the case. The first essay focused on the choice available to firms between arm's length credit and relationship-based credit. The second focused on the Glass-Steagall Act, and the conflict of interest involved when a commercial lending bank enters into investment banking. The final essay examined why indexation of a country's debt, despite offering potential advantages, seldom featured in debt reduction plans.