This data set includes the supplementary material for the article "Kein subjects are hard: Exploring German-speaking children’s behavior with negative indefinites". All content is documented in the README.md file. Abstract: In this paper, we present converging results from three studies investigating children’s production or comprehension of the negative indefinite kein in German. An elicited production study found that 3- to 6-year-old children and adults exhibit different patterns with respect to the production of kein: children, but not adults, exhibit an asymmetry with respect to the position where they produce negative indefinites, in that they use negative indefinites more frequently in object than in subject position. A corpus study investigating spontaneous speech replicated this asymmetry for children, but this time found it also present for adults. Finally, the asymmetry is corroborated by a comprehension study indicating a processing cost for negative indefinite subjects, relative to negative indefinite objects. We argue that these patterns are most straightforwardly captured by an explanation that assumes the decomposition approach to the German negative indefinite kein: rather than a single semantic unit (i.e., negative quantifier), kein is decomposed into a negative part and an indefinite part.