The biggest reason I can think of off the top of my head is that far more people today have debt *because they can* as compared to 1929. Longer mortgages, smaller down-payment requirements, and not-insignificant legal work against instutionalized racism in the banking means that a big component of "more debt" is really just an artifact of 1929's _debt restrictions_.
So there's "more debt" ... so what?
Another item: people sometimes look to "margin debt" as some kind of significant indicator, but the use of this has changed radically. Tax policy encourages people to restructure their finances to use margin debt instead of, for instance, auto loans.
You have $40k and you want to buy a $20k car. Should you:
a) Take out a $16k car loan and pay non-deductible interest
b) Buy $40k of MSFT and write a margin check for $20k for the car,
using your (attractively low!) interest payments to lower your
cost basis of your stock purchase which, by the way, has
appreciated over the 4 years of $300/month payments you make
on the car.
The same obviosuly goes for "home equity loans" ... in the parts of the country which have skyrocketing real estate prices, this is another tax avoidence scheme that "increases debt" in ways you simply couldn't do before but without actually adding to "real" debt.
Other than stuff like that, go right ahead and compare away :-)
/jordan