As I understand, this is exactly what manipluating the federal interest rate is about targeting: they're changing the incentives on different investment types.

As I understand, this is exactly what manipluating the federal interest rate is about targeting: they're changing the incentives on different investment types. When federal interest rates are low, this pushes people to search for other (riskier) investments. Also, I wonder if 401ks and IRAs have that much weight in the grander view of "invested" money saved away, considering their tax-deductability, and thus appeal as a savings plan, is limited and constrained (this year: $18k for a 401k, $5.5K ($6.5K if you're over 50) for IRAs).