I was recently taught the concept of a shinui to be "something done in a way that is unusual compared to the norm in one's area of residence", with respect to the permissibility of actions done on Shabbat and Yom Tov.
My question is "what constitutes the norm"? What if 51% of people do something one way and 49% of people do it another way? Furthermore, what constitutes one's "area of residence" in this matter? Is one's "area of residence" confined to one's home, neighborhood, city, country, state, continent, planet?