Thanks Clive, Nice chart! Those zero cash times were few and far between. The interest on cash would have been pleasant through most of that history.
I note that the "financial crisis" of 2008-9 didn't last long enough to suck too hard on the Cash Straw. That was true of my own activities as well. The "30 Day Rule" kept me from making follow-up buys and so cash dipped but didn't disappear.
The 1968 to 1974 market bottoming with the "Nifty Fifty" is when I was a novice investor just starting off. EVERYTHING I bought went down first!