Likely S/T Newsflow?, page-4

Not only that, the rules change for investment funds in ASX 200, 300 etc. Many funds are legally limited from investing in stocks lower in the rankings in order to maintain their credit rating. This is to prevent some mad money manager of people's pensions taking a punt on a bunch of "penny dreadfuls" and losing everyone's retirement money. This, incidentally, is one of the primary reasons to invest in small caps. Many Big Boys are simply locked out leaving quite a few good chances going begging.