Post-market simulations with box-spreads on the S&P 500 Index show that market ineffiency increased after the 1987 crash.
pˈoʊstmˈɑːɹkɪt sˌɪmjʊlˈeɪʃənz wɪð bˈɑːksspɹˈɛdz ɔnðɪ ˈɛs ænd pˈiː fˈaɪvhˈʌndɹɪd ˈɪndɛks ʃˈoʊ ðæt mˈɑːɹkɪt ɪnˈɛfiənsi ɪŋkɹˈiːst ˈæftɚ ðə nˈaɪntiːnhˈʌndɹɪd ˈeɪɾi sˈɛvən kɹˈæʃ.