Geoffrey Banta
Analyst · SunTrust
Thank you, Allen, and good morning, everyone. I'll make a few comments about our operational performance and trends before turning things over to Janelle to present a summary of our financials.
In terms of underwriting results, we increased our gross premiums written as Allen indicated, by 19.1% in Q4 '11 year-over-year, the 5th straight quarter in which our top line has grown. We also had a good quarter for losses, our premium base claim frequency was down by almost 8% and we had only 4 claims with estimated incurred totals greater than $500,000. This was a much welcome change for us. I'm sure you all have gotten tired of me whining about our bad luck relative to reported losses in fourth quarters past. Happily, this was not the case in Q4 '11.
The fourth quarter increase in top line was due to 2 factors. First, a 6.5% increase in premium on policies written during the quarter, what we refer to as deck sheet premium. And 2, a strong year-over-year increase in payroll audits and related premium adjustments. Our deck sheet premium has now grown for 4 straight quarters and we've had 6 straight quarters of year-over-year increases in our premium adjustments. And importantly, these increases have occurred while we have been increasing our pricing. We also benefited from substantially higher average premium for our new and renewal business, as well as markedly higher renewal premium retention.
Regarding our renewal business, our fourth quarter premium retention was 96.3% versus 79.2% in the fourth quarter of 2010. We believe this provides early evidence of an overall firming of prices in our high hazard niches. Our policy retention meanwhile, was 90.5% in the 2011 fourth quarter, lower than the 93.2% in the 2010 third quarter -- fourth quarter, but a strong figure nonetheless. As mentioned above, our average premium for new and renewal business also increased year-over-year in the fourth quarter from $29,800 to $33,700, an increase of 13.1%.
This increase was due to a rise in average payroll for renewal business and an increased pricing for policies written during the quarter. Relative to pricing, our effective LCM for voluntary work comp in the fourth quarter was 1.56% or 156% of the approved loss cost of the states that use this mechanism for pricing. This was our highest quarterly ELCM since Q1 '06 and it represented a year-over-year quarterly increase of 9.1% over Q4 2010. We have now had a year-over-year pricing increases in all 4 quarters of 2011.
In terms of losses, our fourth quarter results continued to show a slowing of growth case incurred loss development on both an accident and policy year basis. I will break down our loss results in the prior and current accident years.
For accident years 2010 and prior, we experienced overall favorable growth case development in Q4 '11 in that calendar quarter, especially for accident years 2007, '08 and '09. Although 2010 has been a troublesome accident year by itself with unfavorable development throughout calendar year 2011, for all prior accident years, including 2010, we have now had 2 straight quarters of overall favorable development. By the way, we believe that the 2010 accident year, as it moves toward ultimate, will go down as one of the worst accident years for the entire work comp industry.
For our current accident year 2011, the news has been more encouraging as year-over-year claim severity and frequency are down when compared to 2010 and our claims closure ratio is up. We also experienced the lowest number of claims over $500,000 since our 2008 accident year. Due to our pricing actions and the development we have seen in the first 12 months of the accident year, we remained cautiously optimistic about our ultimate 2011 loss experience.
As we move into 2012, we continue to live in a demanding environment for claims management. One characterized by high medical cost inflation, increased medical and pharmaceutical utilization and increased difficulty in returning injured claimants to work in times of high unemployment. We believe these factors will continue to challenge our claims operation and put pressure on claims costs into the foreseeable future. But we are encouraged by lower average severities and loss cost increases in many of our key states in 2011, as Allen discussed.
With that, I will turn to Janelle to present details on our financials. Janelle?