IMDb has stated that to maintain the effectiveness of the Top 250 list they "deliberately do not disclose the criteria used for a person to be counted as a regular voter".[36] In addition to other weightings, the Top 250 films are also based on a weighted rating formula referred to in actuarial science as a credibility formula.[37] This label arises because a statistic is taken to be more credible the greater the number of individual pieces of information; in this case from eligible users who submit ratings. Although the current formula is not disclosed, IMDb originally used the following formula to calculate their weighted rating:[38][39]