ɪt hˈæzbiːn ʃˈoʊn ðæt ˈɛks pˈoʊst ɪfˈɪʃənsi kæn biː ɐtˈeɪnd ɪf ɪnˈɪʃəli bˈoʊθ pˈɑːɹɾiz ˈoʊn fˈɪfti pɚsˈɛnt ʌvðə ɡˈʊd təbi tɹˈeɪdᵻd.
It has been shown that ex post efficiency can be attained if initially both parties own 50% of the good to be traded.