[tomp]

This doesn't make sense - zero interest rates make investment worth more.

10% interest rate => "why invest in this new factory for a 10% return when I can just keep money in the bank?"

0% interest rate => "well if I want to make money, I need to invest"

Feel free to blame other things - maybe 0% inflation rate (higher inflation => more opportunity cost of not investing) or QE (which is similar to 0% interest rates, but still different - a 0% interest rate environment persists since early 2000s whereas QE only started after 2009) which is much more problematic as it floods the market (but not the economy) with money and pushes equity prices through the roof (despite shitty fundamentals).

[danuker]

There is one option you have not looked at:

0% interest rate -> I'll take my money and leave for greener pastures (other countries such as emerging markets).