How sensitive is arrow flight to draw length variation?

Most people shooting long ranges use a clicker to ensure the draw length is not varied from shot to shot.  A change in  draw length changes the arrow speed and hence the height of the arrow at the target.  Without a draw length check variations of a centimetre or so could easily occur and this could be enough, at long range, to move the hit point from gold to white.

A direct answer to the question can only be given for specific conditions but in the note of additional points the following formula is derived

    error = variation*2*A*(1+0.0025R)*R^2/(d*b)

where A is the sight calibration scaling defined in that note, R is the range, d the eye to sight distance and b the difference between full draw and bracing height.  A typical value is found at 90m to be

    error = 53*variation

i.e. a one centimetre variation in draw length gives a 53cm error at 90m.  This is enough to turn a 10 into a 2!