The proposal has been made (Zuckerman, 1999, 2001, with various antecedents) that economy of derivation is operative in language acquisition in such a way that whenever movement appears to be optional to the child, s/he chooses the derivation without movement. In this paper we undertake the task of finding evidence for this claim in monolingual and bilingual acquisition. We draw on data available in the literature and on original data from a bilingual English-Dutch child. This child's word order patterns testify to the fact that movement never occurs beyond the target (e.g. there are no V2 embedded clauses in his Dutch productions), and when deviant word orders are attested they result from lack of raising (in particular, lack of verb raising in embedded sentences in English). These patterns are predicted if economy of derivation holds; further, bilingual children, having as input languages with possibly diverging parameter settings, are especially prone to an extended parameter setting period, giving rise to deviant word order patterns, and thus offering insight into the mechanisms of language acquisition.