The Effective Rate Statistic to Grade Lawn Bowling Performance

Commentators on lawn bowls videos often mention a competitor’s ‘effective rate’. A bowl is commonly seen as 'effective' if it improves the provisional score, i.e. it reduces the count against, converts, or increases the count in favor. This criterion remains fairly valid even in adverse conditions, i.e. when there is a gusty, variable wind, which tends to spread heads because the conditions affect all competitors. An alternative measure, distance from the jack, is strongly affected by weather and rink conditions. Effective rate also remains fairly valid within different levels of skill (i.e. A grade, C grade, etc). Another advantage is that collection of 'effectiveness' data can be done during a competition without intrusion or distraction. Thus commentators can have a running score for the effective rate for every competitor.

A perfect game does not correlate with a 100% effective rate because covering shots, block shots, and other positional bowls may not fit the ‘effective’ definition even though they are tactically correct.

A bowler competing out of his class will lose his matches badly and will have a very low effective rate. To win an end in singles one must achieve at least an effective rate of 25%; that is, the last bowl must convert the head! A bowler can lose an end even if his effective rate on the end is 100% if he bowls first because his competitor can still convert the head and score with the last bowl. The median effective rate thus is likely to be around 62-63%. Top bowlers playing well can have effective rates of 85%.