Diversication: Similar to Mayers and Smith (1990), Choi and Weiss (2005), Cole and
McCullough (2006) and Leverty and Grace (2010), I have measured the concentration of the lines
of business and the states they operate in, using the Herndahl index to express both states and
lines of business. The Herndahl index has been used to characterize the market of each insurance
company in terms of geography and business type. The state Herndahl index for each company
can be written as,