Adherents of Fundamental Indexing (FI) suggest that it is more protable to base portfolio weights on indirectly size-related indicators like accounting data rather than directly on market caps. In noisy markets a la Roll (1984), it is argued, underpriced stocks overperform but are underweighted...

Perold (2007) shows that, given a diffuse prior that is being updated in light of a noisy market price, the posterior distribution says that value-weighting and equal-weighting one's portfolio makes no difference. We argue that the diffuse prior is hard to reconcile with reality and that a...