[maxerickson]

Fannie Mae and Freddie Mac buying 30 year mortgages for decades and decades almost certainly contributed some momentum to housing prices.

I haven't looked seriously for an analysis of it, but it would be interesting to see how quickly the greater affordability of homes (the lower monthly payment from the 30 year) started driving the prices.

[phillmv]

>but it would be interesting to see how quickly the greater affordability of homes started driving the prices.

This was probably one of the leading causes of it.

However, you know what contributed the most? Greenspan lowering interest rates to historical lows in the early aughts and keeping it there for the rest of the decade.

Freddie and Fannie were drops in the bucket. As you said, they bought mortgages for decades and decades without the same problem occurring.

Look up some of this history of the financial crisis. This American Life has a couple good primers.

[maxerickson]

I don't think it is obvious that decades and decades of appreciating home values were unrelated to a housing bubble.

It certainly wasn't the immediate cause, but I think it probably helped set the stage (it would be really interesting to have an alternate Earth where we could look and see what happened without that particular government meddling).