It’s estimated [3] that the pound sterling made up around 64% of the world’s official FX reserves in 1899. It had fallen to about 48% by 1913. As you'll likely glean from the graphic below, Addogram notes [4] that historic recurrence seems to like operating in base-100 when it comes to reserve currencies. The dollar's share of global (official allocated) FX reserves has fallen from 72% in 1999 to 62% at present. As we have pointed out before [5] - reserve currency status doesn't last forever...
The center of each “dynamic” pie chart below shows the composition of official (allocated) foreign exchange reserves in 1999. The further you move outwards from the center, the closer you draw to the present day.
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Chart: Addogram [4] [4]