How often is the stock market at its all-time-high?

So I’m reading this book on investing, and the author is arguing strongly against timing the market. Whether or not timing the marked is a good idea is beside the point here (it probably isn’t), but a particular statement caught my eye. In the German translation of Peter Mallouk’s “The 5 Mistakes Every Investor Makes and How to Avoid Them”, the author says:

Viele lassen sich von Schlagzeilen darüber abschrecken, dass sich “der Markt auf einem Rekordhoch befindet”. Das stimmt sogar häufig, es ist jedenfalls keine Seltenheit.

…which roughly translates to:

Many are scared off by headlines saying that “the market is at a record high”. This is actually often the case, at the very least it is not a rare occurrence.

I wanted to dig a little deeper here, in particular, answer the following question:

How much of the time have stock markets been historically near the top of their highes valuations?

Let’s fire up a Jupyter notebook, grab Pandas and the good old Matplotlib and find out.

You can find this notebook over here on Github.

So what does it all mean?