The hottest topic in Silicon Valley is the rise of the so-called unicorns -- privately-held tech companies valued at $1 billion or more.
Unicorns are coming to life in many of the globe's leading economies, but not in Japan. The U.S. has 112 of the 222 such businesses, Japan has just one, according to the research group CB Insights. China has 59, and India has three. Why such a yawning gap between Japan and other big economies?