Excluding the impact of the valuation allowance reversal in 2012, the Company's effective tax rate for the third quarter of 2013 was 36.6% compared with 33.4% for the same period a year ago, and 38.2% for the first nine months of 2013 compared with 32.8% for the same period in 2012. The year-over-year increase in the effective tax rates primarily reflects the higher tax benefits from tax exempt municipal interest relative to pre-tax income in 2012 as compared with 2013, as overall earnings improved in 2013.
Total assets increased $95.2 million, or 9.0%, to $1.2 billion at September 30, 2013 compared with a year earlier. The increase in total assets was primarily the result of growth in the investment security and loan portfolios. Total stockholders' equity was $125.1 million at September 30, 2013, a decrease of $17.2 million or 12.1%, compared with a year earlier, primarily due to the repurchase of the Series A Preferred Stock and related warrants from UST, and to a lesser degree declines in accumulated other comprehensive income due to erosion in the fair value of the investment securities portfolio as interest rates have recently risen causing a steepening of interest rate yield curves. These declines in stockholders' equity were partially offset by an increase in retained earnings attributable to the continued positive earnings results during 2013.
Total gross loans increased $98.8 million, or 14.6%, to $777.2 million at September 30, 2013 from $678.3 million at September 30, 2012, resulting from strong growth in commercial, residential, and agriculture lending relationships. Total new loan production, including mortgage loans originated for sale, increased $8.4 million, or 7.6%, to $119.2 million during the three months ended September 30, 2013 compared with $110.8 million a year earlier. Total deposits grew $101.9 million, or 11.9%, to $957.0 million at September 30, 2013 from $855.0 million a year earlier as we continue to build on our existing strong customer relationships and establish new customer relationships.