Methodology



  • Data


    • Test scorecards from 1877 to date are parsed to rate every bowling performance.

    • Scorecard information is sourced to generate an accurate assessment of each player's performance.

    • Match results are used to generate team ratings. Peak ratings are identified by checking if the rating before and after the particular match considered is lower.

    • Fielding performances are evaluated by parsing detailed text commentary. More detail here.

    • Win shares are calculated by attributing over-by-over team match odds changes to the appropriate player.

    • Players lose 1% of their live rating if they miss a team match. This is to ensure injured or dropped players do not stay high in the ratings without playing matches.

  • Ratings


    • Current Top Test Bowlers:
      This is evaluated using a weighted average of a bowler's performances. More weight is given to recent performances with past performances diminishing in value with time. Unestablished bowlers that have played less than 20 innings are penalized to avoid cases where a few highly rated innings can catapult a newer bowler to the top of the pile.

    • Best Test Bowling Careers:
      This evaluates overall careers by calculating the average performance rating of each bowler, with a bonus given to career longevity (where playing the most number of years while missing the least percentage of matches gets the most credit) and a penalty for careers of less than 40 matches (increasing penalty for lower matches played). The 95% confidence interval range is shown with a ± after the career rating.

    • Best Test Bowling Performances:
      This is a list of the highest rated bowling performances calculated using the factors given below.

    • Best Test Team Bowling Peaks:
      This lists the best bowling attacks by aggregate current bowling ratings of the first 5 players that bowled for the team in a match. Only peaks (aggregate rating before and after lower) are shown for clarity.


  • Performance Factors


    • Wickets per run: This is a major factor that gives the highest value to a high number of wickets taken with the least runs conceded. By tieing the factor with runs conceded this avoids rewarding wickets taken after conceding a significant number of runs.

    • Wickets per ball: This is also a major factor that gives the highest value to a high number of wickets taken with the least number of balls bowled. This rewards strike bowlers that are very valuable in test matches.

    • Economy: Minor factor that rewards bowling a long spell of tight bowling where only a few runs are scored. This is to distinguish between bowling innings where a bowler bowls well for long periods with no reward but keeps the pressure.

    • Wickets quality: Major factor that considers the total current batting rating of the batsmen dismissed. The rating is adjusted to consider the runs scored by the batsman and the total runs conceded by the bowler to specifically reward the bowler for getting highly rated batsmen cheaply. Minimal credit is given when a batsman has already made the runs expected of him based on his rating.

    • Batting quality: Moderate factor that considers the current rating of the batting line-up faced. Adds increasing value to more significant bowling performances to avoid rewarding unsuccessful and expensive returns against good batsmen.

    • Pitch quality: Moderate factor that considers total runs scored by the opposing team to quantify how easy or difficult run scoring is in the match. Adjustments are made for the innings number using historical average scores.

    • Incomplete innings: This factor comes into play significantly in incomplete innings (< 75 total overs bowled). If the bowler has bowled less that 15 overs and conceded less than 50 runs, it is deemed an incomplete performance where he did not get the opportunity to make an impact. In these cases, the bowler's current bowling rating overrides the innings performance to avoid unduely penalizing the performance. This functions similarly to a batsman being not out at the end of an innings.

    • Location: This is a minor factor that adds a bonus to significant performances completed away from home.

    • Match status: This factor rewards match-winning or match-savings performances made under pressure in the second innings. Significant contributions in successful fourth innings defenses and third innings come backs get the highest values.

    • Series status: Minor factor that adds a bonus to bowling performances in a series decider and a penalty to performances in dead rubbers.

    • Result: This factor recognizes significant contributions made in wins and draws. Positive results against higher rated teams are rewarded more than against lower rated teams, using the current rating at the time of the match of the opposition team.

    • Close match: Rewards significant contributions made in close wins in terms of wickets or runs left. Recognizes performances that are remembered for delivering under pressure.

    • Milestone: Minor factor that adds a bonus to bowling performances with at least 5 dismissals.