Share the gain, share the pain? Almost transferable utility, changes in production possibilities, and bargaining solutions

► Generalized Utilitarian Bargaining solutions (GUBS) violate solidarity. ► Cardinal properties of individuals' utility functions matter for GUBS. ► We introduce ATU, a utility domain that shares with TU the same ordinal properties. ► ATU allows for a much broader range of cardinal properties than TU. ► We prove that GUBS satisfy solidarity if and only if utility profiles satisfy ATU.