jˈɛt, ˈɛks pˈoʊst ɪfˈɪʃənsi kænˈɑːt biː ɐtʃˈiːvd ɪf ðə sˈɛlɚz ʌnəbzˈɜːvəbəl ɪnvˈɛstmənt ˈɪŋkɹiːsᵻz ðə bˈaɪɚz vˌæljuːˈeɪʃən, ˈiːvən ɪf ˈoʊnli ðə bˈaɪɚ hɐz pɹˈaɪvət ˌɪnfɚmˈeɪʃən ɐbˌaʊt hɪz ɔːɹ hɜː vˌæljuːˈeɪʃən.
Yet, ex post efficiency cannot be achieved if the seller's unobservable investment increases the buyer's valuation, even if only the buyer has private information about his or her valuation.