Iowa companies paid $674 million in workers’ compensation premiums last year, a 12.7 percent increase from 2011.

This year, the insurance division phased in a 7.7 percent increase in both the voluntary and assigned risk categories by increasing the rate in January and again in July. The overall average voluntary rate has increased in each of the past four years by as much as 9.1 percent and last decreased in 2009 by 3.8 percent. The division is considering an average 2 percent decrease in 2014 for the voluntary rate, which is paid by most companies. 

Here’s a look at how total written premiums have increased, and the largest writers of coverage in the state.