Once a symbol of American commercial dominance, Nike has seen 78 percent of its market value erased — a collapse severe enough to end its membership in the S&P 100 Index, effective September 21, 2026. What the swoosh once represented — the certainty of brand power, the durability of premium positioning — is now a study in how quickly institutional confidence can dissolve. The index exit is not the wound itself, but the formal record of how deep the wound has become.