Why is Japan selling bonds with negative interest rates?
http://archive.is/bbKzj
TL;DR:
Japan is venturing into deep uncharted waters by issuing bonds that will actually cost buyers money over their 10-year lifetime. With this, Japan has joined the elite group of a few EU nations (like Sweden) that have done something similar. The return on the bond is -0.5%.
But with the financial markets in turmoil, many buyers are willing to put their money into it. Like many other central banks, Bank of Japan had been cutting their interest rates to stimulate the economy. After reaching zero, they had to go negative.
However, Bank of Japan's past use of monetary policy to produce stimulus has produced almost no results. This move to negative rates, may also encourage other nations to try it. This may trigger currency wars.