As hyperinflation accelerated, the value of the Zimbabwe dollar declined fast against other currencies, yet official exchange rates published by the Reserve Bank of Zimbabwe were infrequently updated; this made it impossible to tell from an official source how much the Zimbabwe dollar was really worth against other currencies on a particular day, which in turn disrupted international business transactions involving Zimbabwe dollars. Staff from WM/Reuters devised an indirect means of measurement that was termed the Old Mutual Implied Rate (OMIR).[26] This took the daily price of shares in the insurance company Old Mutual that traded in the London and Harare stock markets and derived from it a notional daily exchange rate between the Zimbabwe dollar and the pound.[27][28] Shares had much less strict capital controls than through the Zimbabwe banking system, so the shares were used as a vehicle for moving capital between currencies by buying stock in either London or Harare and then selling in the other location.