What are the rationales as to why investors would buy negative yielding bonds?

-Investors bet that the market interest rates may fall further in the future.

-Investors think that they may be able to sell the bonds later on to someone at a higher price when the market yields rise.

-The Central Bank purchased a large amount of government bonds, causing the bond's price to rise and yield to fall to subzero.

-For large asset management companies in Europe, holding funds in cash is more costly because banks in Europe charge large depositors to hold money in savings.