Fourth quarter commission expense was $18.5 million compared with $13.7 million in 2011. Commission expense increased primarily due to the higher net premiums earned and higher agency incentive commissions due to increased agent production in 2012 compared to 2011.
Our Underwriting and other operating expenses ratio declined 1.8 percentage points in the fourth quarter year over year as we continued to increase premium and scale. Overall, underwriting and other operating expenses were $30.5 million compared with $23.5 million in the fourth quarter of 2011, an increase of $7.0 million, primarily as a result of a $5.0 million increase in equity and incentive related compensation expenses and a $1.9 million increase in premium taxes and assessments as net premiums earned increased. These increases were partially offset by a $0.4 million decrease in professional services fees compared to the same period in 2011. Additionally, implementation of the new accounting guidance for DAC resulted in a $0.6 million increase in our underwriting and other operating expenses for the three months ended December 31, 2012.
An income tax benefit of $1.4 million was recorded in the fourth quarter of 2012 compared with an income tax expense of $6.6 million in the fourth quarter of 2011. The tax benefit was primarily related to increased non-taxable income resulting from the favorable LPT reserve adjustment and the LPT Contingent Commission Adjustment, both of which were tax exempt.
At the end of the fourth quarter of 2012, the year over year change in net rate was a positive 8.3%, continuing the positive trend in net rate begun in the fourth quarter of 2011. The net rate change in California was an increase of 13.7% year over year. Our change in total payroll exposure increased 25.9% year over year.The fourth quarter 2012 combined ratio was 51.4% (112.5% before the impact of the LPT), compared with 110.6% (115.4% before the impact of the LPT) for the fourth quarter of 2011. Year over year, the combined ratio before the LPT improved 2.9 percentage points.