US sanctions barring American investors from owning or trading in stocks allegedly owned or controlled by the Chinese military could deal a serious financial shock to millions of retail investors and pensioners in Hong Kong. The Tracker Fund, the biggest and most popular exchange-traded index fund in the city, has a dramatic U-turn within three days on its investment in several major Chinese-owned firms to its portfolio, because it is managed by a US-based company that must abide by the sanctions.