Note from dshort: The NYSE has released new data for margin debt, now available through May. I've updated the charts in this commentary to include the latest numbers. The New York Stock Exchange publishes end-of-month data for margin debt on the NYXdata website, where we can also find historical data back to 1959. Let's examine the numbers and study the relationship between margin debt and the market, using the S&P 500 as the surrogate for the latter.