Most investors are generally aware of the reflationary effects of QE conducted by the U.S. Fed.
It is reasonable to imagine that, in announcing its intent to embark on Europe's own version of quantitative easing, the ECB anticipates a similar effect with respect to European equities. Taking into account the plan for EUR 60bn a month in purchases (beginning in March), the ECB's balance sheet expansion should look something like this:
When we overlay the MSCI Europe, we find a somewhat surprising relationship-- equities have risen as the central banks' assets have contracted over the last several years, implying that asset purchases (inverted on the following chart) could actually be negative for stocks:
We have no way of knowing for sure whether or not this pattern will hold, but this chart would seem to suggest that MSCI Europe equities could decline ~30% by the end of 2016.