Abstract This work is a first tentative step towards motivating constraints on movement as a mechanism for minimizing grammar size.

Recently is has been proved that every Minimalist grammar can be converted into a strongly equivalent single movement normal form such that every phrase moves at most once in every derivation. The normal form conversion greatly simplifies the formalism and reduces the complexity of movement dependencies, but it also runs the risk of greatly increasing the size of the grammar. I show that no such blow-up obtains with linguistically plausible grammars that respect common constraints on movement. This provides an entirely new, quantitative motivation for movement constraints.