It seems likely that the longer a survey is open, the more people will take part. But the data does not support that seemingly commonsense notion. For a group of 34 surveys selected by mostly because they all state the duration of the survey and the number who took it, the correlation between the number of weeks open and the number of participants was a negative 0.2! The shorter open periods were associated with more taking part!
What drives numbers of participants more than length of time open depends more on the quality and size of the email invitation list. By “quality” we mean that the invitees have a reasonable chance of being interested in the survey; the list isn’t some random collection of email addresses. By “size” we mean the sheer number of invitees; all things being equal, if more people receive the invitation, more people will decide to complete it.
Other factors that drive participation rates likely include whether the invitees know and respect the law firm (or co-contributors), the time demands of the survey, the topic, and the level of the invitee (senior executives and general counsel are bombarded with requests to complete surveys, but more junior people may receive invitations rarely and be more willing to participate).
The scatter plot below shows along the bottom axis how many months a survey was open and along the left, vertical axis how many participants completed it. Open periods of one month or of two months were the most common. For all of these surveys, with 8,500 total participants and 56 total months open, the average number of participants per month was 152.
We will need more surveys to derive dependable numbers on averages per month, and likewise to look at averages of participants per season.
Does seasonality influence participation numbers? Does it make a difference in what month you launch your survey? The next plots tells us that firms had no particular favoritism, except that none of them triggered their survey in the middle of summer, in July.
Institutional calendars, workload, or summer vacation plans may account more for the starting month of the survey than sensitivity to what will maximize participant numbers. Law firms may have budgets based on fiscal years or they may orient their survey toward a conference or try to catch the wave of heightened interest in a topic