A canal division holds that lining the earthen field channels with cement is what cut the water lost between the outlet and the fields in the twelve villages where the work was done. Which of the following, if true, most strengthens the division's position?

A cause worth believing in should give more where more of it is applied, and that is what the village-by-village figures show — the saving rises and falls with the length lined, and vanishes where no lining was done. A general fall across the district could have had many sources; a fall that tracks the treatment dose for dose has very few. One contractor, an old entry in a list of works and the practice of other states say nothing about how the saving was distributed here.