Each quarter, after data collection ends, I send emails to those with a gap in their responses seeking to close said gap. This time around, these emails went out to 50 members who responded for June and in earlier quarters, but who missed either December or March. Just a couple percent of the total, but still well worth doing.
For example, take someone who responded in September, December, and June, but not in March. Without filling the gap, only September through December and the month of June could be included in the analysis–five months. Once the member fills in the gap, usually by communicating that no repairs occurred during it, January through May can also be included, five additional months. So a single simple response doubles the amount of data for this particular vehicle.
Aside from increasing the amount of data, filling the gaps yields more accurate results. Rarely does someone report a repair in response to these gap-filling emails. It seems that when people fail to respond, it is because they had nothing of obvious significance to report. But it is just as important to know if there have been no repairs. If the gaps were left unfilled, the resulting repair rates would be a bit higher than they should be. So we strive to fill as many as possible.