This study proposes a novel solution concept--the w-value--for cooperative games with public externalities. The w-value is axiomatically founded on three principles: Pareto Optimality (PO), Market Equilibrium (ME), and Fiscal Balance (FB), which together ensure a fair and economically sound distribution of gains. We establish its existence, uniqueness, and an accompanying implementation mechanism. A key theoretical advantage is its strong stability: the w-value lies within the core, specifically...