Not sure I understand your objections - there's no analysis in the chart (raw #s in the chart I posted - no deflator) - it's just data drawn from nyxdata website juxtaposed against the index. As to linear vs % vs constant dollar, etc., they slice it all ways and the basic point of margin peaks correlating to (no one's making a causal argument) index peaks holds. Your point about market corrections leading to reductions in margin exactly fits my point: high prices attract buyers; higher prices get them levered up; lower prices get them liquidated. Interest rate fixing certainly exacerbates the problem and sets up the conditions for a bigger fallout this time.

Here's another view in inflation adjusted %'s.