The standard problem with using the Drake Equation and similar formulas to estimate how much of the Great Filter is in front of us and how much is behind us is the lack of good estimates for most terms. However, there are other issues also. The original version of the Drake Equation presupposes independence of variables but this may not be the case. For example, it may be that the same things that lead to a star having a lot of planets also contribute to making life more likely (say for example that the more metal rich a star is the more elements that life has a chance to form from or make complicated structures with). What are the most likely dependence issues to come up in this sort of context, or do we know so little now that this question is still essentially hopeless?