A Time Series Analysis of Noninterest to Interest-Earning Dynamics Between 1984 to 2023 in the US Commercial Banking Sector

Both interest and noninterest earnings form the two critical components of the income stream of commercial banks. While interest earnings are tied to the lending volume and prevailing interest rates primarily dictated by the monetary policy and central bank interventions, noninterest earnings can come from diversified sources like income from fiduciary activities, trading revenue, service charges on deposit accounts, fee income, etc. Noninterest earnings can be unrelated to lending volume and prevailing interest rates and possibly uncorrelated with the monetary policies. Noninterest earnings may be a more robust source of income, especially during the low-interest rate regimes. Managing the noninterest to interest earnings is a critical component of income smoothing used by the banks. Noninterest earnings have become a significant component of banks' overall earnings in the last four decades, and the ratio of noninterest to interest earnings has also grown significantly, raising questions about the primary role of the banking sector in financial intermediation as defined by the collection and disbursement of loanable funds throughout the economy. The rise in noninterest earnings also raises questions about the potential conflict of interest especially if banks earn significant consulting income from the same entities that borrow heavily from the banks. In this paper, I look at the time series dynamics of the ratio of noninterest-to-interest earnings spanning nearly four decades from 1984:Q1 to 2023:Q3 for the USA's FDIC-insured commercial banking sector. Although the ratio has fluctuated over the period and risen from the baseline, it does not exhibit any non-stationarity. The presence of unit root cannot be found during the time period studied. In other words, the ratio of noninterest-to-interest earnings in the US commercial banking sector does not show any explosive and unstainable growth. In a nutshell, the rise in the ratio seems to be an outcome of the broader income diversification strategy used by the banks and not necessarily a dramatic change in the business model of US commercial banking industry.