The naturalness with which case ellipsis occurs in certain environments in Korean has been attributed to the information status and markedness of arguments. In recent accounts of case ellipsis in colloquial Korean proposed by Lee (Lang Res 42:323–355, 2006a; J Pragmat 39:1465–1481, 2007) and Kim (PhD dissertation, 2008), the effects of these factors on case ellipsis have been subsumed under iconicity of complexity. In this paper we argue that iconicity plays no role in stating and explaining patterns of variation in case ellipsis and propose an alternative usage-based explanation in terms of economy. This proposal subsumes and clarifies previous findings about the influence of the factors of contrastiveness, animacy, and definiteness and connects these findings to asymmetries in frequency and predictability. In addition, the economy account leads to a number of other predictions that the iconicity account does not make, including differences in the direction of the effects of contrastiveness and animacy/definiteness and differences between subject and object marking. Using evidence from two rating experiments, this paper also demonstrates that preference for case ellipsis on three subtypes of focused objects (selecting, replacing, and informational focus) increases relative to the degree of predictability whereas average ratings between sentences with these subtypes of focus subjects do not show a statistically significant difference. This finding is not consistent with the prediction of the iconicity-of-the-complexity principle and cannot be accounted for in terms of the dichotomous distinction between contrastive vs. non-contrastive focus. This paper is the first demonstration that the gradient pattern of case ellipsis shown by subtypes of focus can be explained in terms of asymmetries in frequency and predictability, i.e., the economy principle, and suggests that it may be possible to explain the effects of information structural factors and animacy/definiteness on the ellipsis of case markers for both focused and non-focus arguments entirely through the economy principle.