Financial speculation and bubbles? are often of vital importance in fueling technological progress. Janeway reviews and distinguishes between various kinds of speculative bubbles over the past two centuries. While many have been unproductive and all have crashed, some bubbles have had a long-run productive impact by spurring investment into real capital and new technology (e.g. railways, electrification, computers). Financial bubbles can often help close financing gaps when venture capital by itself would otherwise have fallen short, and thus have played an instrumental role in accelerating technological innovation.