how rates are determined
the wm reuters benchmark rates are determined over a five minute fix period from 2 minutes 30 seconds before to 2 minutes 30 seconds after the time of the fix which is generally 4 p m in london during this five minute window bid and offer rates from the order matching system and actual trades executed are captured since trades occur in milliseconds only a sample is captured rather than every trade the median bid and offer are calculated using valid rates over the fix period and the mid rate is then calculated from them 1 the importance of these rates lies in the fact that they are used to value trillions of dollars in investments held by money managers and pension funds in 2013 the method of fixing the wm benchmark rates came under intense scrutiny after widespread allegations of collusion and rate manipulation by traders surfaced 3 