"A simple way might be to add up:
- non-insurance earnings
- look-through earnings (using Bloomstran's)
- interest income ("Other")"

"Average: 7.0%
A clear downtrend, as expected."

As discussed previously, the book value growth in the last 5 years is 11.5% CAGR.

rochish replies on IV and growth estimates

Clearly, there is a big disconnect between the metrics the firm is using to calculate book value and the above three metrics you mentioned. Are you missing anything that the firm considers relevant to calculate book value?

What multiple are you using on the look-through earnings? Assuming you use a single multiple for all their businesses (from railroad to energy to insurance to manufacturing and services, etc.), is that a valid approach?

I think the firm uses the current market value of equities for purposes of book value calculation. Fully owned subsidiaries are included at the cost of purchase (barring write-downs, etc. such as the 10B write-down on Precision Castparts some years ago). Unless one can argue that the equities held by BRK are overvalued, that seems to be a more reasonable approach to me.