Operating revenue driven by the Company's investment subsidiary, Rockville Financial Services ("RFS"), increased by $28,000, or 37%, from the linked quarter. While not a significant component to the quarter's results, noteworthy is the evolution of this business line to include four new financial advisors. At year-end this division was comprised of five full time financial advisors and one full time sales assistant with a combined 80 years of industry experience to better serve the needs of Rockville's customers and branch network. The Company has recently re-aligned its advisor territories to better serve its existing RFS clients. The new West Hartford Banking Center will have a dedicated full time financial advisor who is a Certified Financial Planner.
Net interest income was stable and increased slightly by $63,000 to $17.0 million in the fourth quarter compared to the linked quarter. Average earning assets increased by $33 million, or 2%, due to continued business development resulting in commercial loan growth and strategic decisions to increase available for sale investment purchases. The tax equivalent net interest margin for the fourth quarter of 2012 was compressed by 6 basis points to 3.74%, compared to 3.80% for the third quarter of 2012 as a result of the 8 basis points decline in the tax equivalent yield on interest-earning assets outpacing the 3 basis points decline in the cost of interest-bearing deposits. The reduction in the average yield during the fourth quarter from both a linked quarter and year-over-year basis, was primarily attributable to the impact that the extended low interest rate environment has had on the yields of new loan originations and adjustable rate mortgage repricings. The cost of interest-bearing deposits decreased across all comparable periods as a result of the Company's continued focus on growing low cost core deposits, particularly with the commercial banking expansion, and on reducing the cost of funds as well as the continued migration out of time deposits to other interest bearing deposit types. The Company's strategic decision to take steps to shorten the duration of earning assets during the quarter while extending funding will better position the balance sheet for rising interest rates and enhance its long-term earnings but will adversely impact short-term earnings.