My instinct tells me that the survey is only a mirror of reality, not its deep cause. The 75% of travelers who verify their papers in advance do so out of pragmatism, a habit dictated by experience to avoid last-minute troubles, well before any survey. It's like my tenants who meticulously prepare their documents for a police cita previa. What would disprove this perception is to observe a significant change in this behavior after the publication of such a survey, not before.