Percentage of shares held (controlled) by larger investors.
Institutional holdings percentage is a very important piece of information to be aware of when it comes to making a trading or investing decision. Examples of these types of holders are insurance companies, hedge funds, mutual funds, endowments, and investment advisors. The higher the % of a stock these players control, the easier it is for them to control the movement of a security (manipulate it via light buying or simply not sell, maintaining the price). Its tough to short sell (bet against) stocks like this because they have most of the supply locked up and therefore if they simply do not sell, the stock will not drop. Retail trading of the remaining available shares may not have much influence. If the float is very small, the stock can very easily be controlled and pushed higher. As it ticks up these whales holdings become much more valuable. Obviously there is a strong motivation to do this and it does happen. Remember that the majority of daily trading volume is via whales not retail traders. SPY ETF (to the right) is a great example. It is locked up by huge players like JP Morgan, Goldman, Bank of America, and Citadel. Its no wonder the thing just wont come down as of this writing.
Related to your trading:
When you do your due diligence and are seeking out a stock for trading or investment, it is wise to always know what you are dealing with. Discover the institutional interest % and take a look at the players. If you are looking at a short, then you need to be aware of someone like JP, Fidelity or Goldman holding a large block. These are not the type of people you want to bet against in most cases. Clearly, it is in the best interest of some powerful players with big money to keep it afloat. If the institutional percentage is high (above say 50%) then there is a good chance the stock will get higher on solid news and hold up very well. Likewise, if there was extremely bad news there could be enormous outflow. Chipotle (CMG) is a great example of a stock with high institutional interest - 96%. When this stock has positive news it climbs and can hold price extremely well. Always be aware of this info and be sure to use it to your advantage when making your next move!