This is a similar image I did in late January, which shows 1- and 2-standard deviation lines above the smoothed "value" line, being the variation of how well it fits the price history. I haven't done an updated one since then.
https://www.stonewellfunds.com/SmoothedRealValuePe...

Here's an update to that graph. The yellow spot is Friday's close.
https://www.stonewellfunds.com/SmoothedRealValuePe...

The smoothed value line further up the thread is based on book per share only.
This one is the the simple average of [a multiple of book] and [my own valuation method which is basically investments per share plus a multiple of net income on non-investment stuff].

Until fairly recently the two methods gave almost identical results, but operating earnings have been pretty weak compared to investments&book in the last ~3 years, so my own valuation level is lower than the multiple of book. In the last 3 years, my WMA of real book is up 7.1%/year, but WMA of my own valuation method is up only inflation+ 3.9%/year, so the blend of the two on the graph is up 5.5%/year. As a result, the recent slope of the smooth line in this graph is a bit shallower than what you'd get with a multiple of book alone.

Anyway,
* Log of market price, inflation adjusted, log
* Log of a smoothed value line, inflation adjusted, scaled so that the 20 year average is closest to observed market price
* Plus and minus 1 and 2 standard deviations of the value line - variation versus market price

Friday's close is 16% (1.27 standard deviations) above this particular smoothed value line. In the past, a result like that (in the top 15% of the time of valuations on this metric), average four year forward returns were inflation + 2.1%/year. But of course valuation levels in future may not resemble those of the last 20 years, and my valuation methods may be a load of hooey, and nobody knows yet how Berkshire's value will evolve in the next few years.

Jim