More thoughts inspired by David Halpern's The Hidden Wealth of Nations.
The "declarative norm" is what we perceive others to be doing. We are much more likely to do something if we think that "everyone is doing it."
I have always thought that one of the distinctive functions of sociology is to show people the true proportions of every practice - everyone is not doing it (whatever it is); X percent are doing it, but you could choose to be in the Y percent who are not.
The government often makes the big mistake of inflating a problem to get more attention. However, this strategy makes it more likely that people with think that problematic behavior is the declarative norm, which makes them more likely to do it.
I believe that of all the big mistakes government can make, promoting the culture of fear as the declarative norm is the biggest mistake of all.