Note: This question was written for the weekly topic challenge.
Many of you who deal with asset allocation will probably already be familiar with Mebane Faber's Timing Model, based on one of SSRN's most popular papers of all time, A Quantitative Approach to Tactical Asset Allocation. The crux of his approach is to apply the momentum approach to the decision of when to switch between major asset classes.
What are some of the other major contributions to market timing? What other approaches do they use?