An index presented in the book: The Dao of Capital by Mark Spitznagel.

How is it
calculated?

The MS index is the expected return on invested capital (equity) divided
by the invested capitals replacement value (net worth), and can be calculated
for the U.S. as follows.

The Z.1 Federal quarterly reports give us the data we need. On table B.103
(Balance Sheet of Nonfinancial Corporate Business) line 40 holds the market
value of equities outstanding and line 39 holds the net worth.

These reports only come out each quarter, therefore we want a way to estimate the MS Index in
the meantime. We can use the U.S. stock market value (S&P
500 Index) to estimate U.S. corporate equity and the most recent Z1 net
worth number to estimate the current U.S. corporate net worth. (This causes the sudden change in the 1 year graph.)

The final step requires us to scale the index values by the geometric mean (P.231 Dao of Capital). To do this,

Multiply all index values together

Take the nth root of step 1 (n being the number of index values)

Divide every index value by step 2 (step 2 is the graph's geometric mean)