Dative Substitution is one of three types of variation found in Icelandic subject case. It affects verbs with experiencer subjects and consists in the original accusative subject case being substituted by dative. Previous research indicates that intra-speaker variation is a widespread consequence of this change. The study presented in this paper was designed to document the distribution of the variation, focusing on pronominal subjects with the verb langar (‘want’). The data consist of naturalistic data collected from Google searches and blogs and elicited judgments obtained with an online survey (280 participants). A pilot study on variation in language acquisition was also conducted. The results indicate that grammatical factors affect the distribution. The rate of DS differs depending on the person and number of the subject. Nominative-accusative syncretism in the inflectional paradigm of the subject also seems to matter. I argue that the variation is part of the grammar and suggest that children acquire it through a probabilistic model of learning.