A detailed mathematical expression is proposed by Parkinson for the coefficient of inefficiency, featuring many possible influences. In 2008, an attempt was made to empirically verify the proposed model.  Parkinson's conjecture that membership exceeding a number "between and " makes a committee manifestly inefficient seems well justified by the evidence proposed. Less certain is the optimal number of members, which must lie between three (a logical minimum) and 20. (Within a group of 20, individual discussions may occur, diluting the power of the leader .) That it may be eight seems arguable but is not supported by observation: no contemporary government in Parkinson's data set had eight members, and only the unfortunate king Charles I of England had a Committee of State of that size.