But at the same time an increase in short interest could be interpreted as a bullish sign, since it represents potential future stock purchases.

Finally, some of Japan's bullish signs don't stand up to close inspection.

Conversely, these analysts see a drop in short interest as a bullish sign.

Strong employment numbers are generally considered to be a bullish sign.

And that has to be a bullish sign for bonds.

"That means there's $50 billion on the sidelines waiting for the market to stabilize," which he called a bullish sign.

Investors viewed today's news as a bullish sign for the economy.

Conversely, these analysts say a drop in short interest is a bullish sign.

A wave of reverse splits at substantial companies, for either reason, could be a bullish sign.

But many investors consider a rise in short interest a bullish sign of potential future buying power in the market.