There is no sure way of getting the exact to the point value of an insuarer but there ways of leting you know if they are over, fair or under valued.
Valuing an insuarer especially in the Property and casualty business isn't as hard as you would imagine. You just have to know the value drivers and use them to value the business.
So what are the value drivers? Simple!
1. Good Underwriting margins
2. Prudent investing to create an income stream(Investment income)
3. Prudent investing to compound capital (Capital appreciation).

Now a good insurer is one that focuses on those 3 in the same order. Because, you cant time the market, hence you prefer building cashflows and you cant build cashflows without having float and building it.
So with that in mind, it becomes easy to value an enterprise.
1. Whats the historical combined ratio? For starters, you want company that can have underwriting margins of 5% and above. And you want to have at least 6 out of 10 years for positive underwriting margins(it builds the float.)
2. Consider the premiums written in the last 5yrs and estimate the average,and make it a per share figure.
Say 5yr average premiums written are 2,281,106,200 and the company has 5m shares. Therefore the value would be 456. Now assuming historically they have had say 5% underwriting margins, then that would be 23. (for safety you can use their worst positive underwriting margins).
3. Consider the investment income. Remember, you cant predict share price oscillations but you can estimate what interest the CBK would pay or prevailing yields on high quality bonds. Consider the income the investments throw off per year and add that to the underwriting margin. So look at the balance sheet at bonds and get that value and multiply it by the prevailing yields.(For safety, you can use the lowest yields). Now this company say it had 1,044,663,000/- in gov't and Corporate debt. You can multiply them by say 7% to get 73,126,410/-. Compare that with the average investment income for the last 3 years and take the lower of the 2(in this example, average investment income has been 178,269,000). Make the figure into a per-share=15/-.
4. You add the pershare underwriting margins to the pershare investment income= 38. This is the average pretax earnings per share.
Now you can attach a p/e to this and remember to be conservative in your estimate. Say you attach a P/E of 6 then the value would be 228.
Remember thats an estimate and before reaching this way, you need to be certain that the insurer passes all other qualitative feautures like good management, prudent pricing and good risk management.
You can compare this figure to the actual variables e.g, say you use the actual 3 yr average investment income, or if long term underwriting margins have been greater/ less than 5%. Test the hypothesis. Then compare that with other metrics like book value.
If there is a great discount to all estimates, start shooting!

What are you 'screaming' for people to buy now?

@msimon I just read this post and was disgusted.

Are you aware that jubilee changed its name from jubilee insurance to jubilee holdings.
The reason for this is the inclusion of investment in its core business..
So for you to say that they would have announced a loss without investmeny income is like saying safcom would announce a loss without its income from data and mpesa..