Public opinion on issues such as gay marriage, immigration, free arms sale, driving license for women may remain unchanged for decades and then suddenly change. Sociologists are trying to understand if there are rules as to how masses of people change their mind over certain issues. It was thought that to change people’s opinions a consensus of at least 50% was required. A recent study says that when 25% of a group of people takes a firm view on a certain matter this becomes a critical mass for change that changes the remaining majority. For sensitization efforts to reduce sexual harassment on the work place, bullying, waste disposal without separation, physical inactivity, smoking, drinking while driving, to be successful at least one quarter of the population must believe in the change. This is a driving force even when the ‘remainers’ are offered incentives not to change idea. Naturally, those in favor of a certain change do not know how close his/her group is to becoming a critical force. Clearly, this is a crucial piece of info, because if close to 25% just a few more people, are essential to save or change a certain norm. However, this info is in the hands of those who know how to handle data and use the relative technologies. An exception to the 25% rule is ‘the age of a certain idea’. If old, then you need a little bit more than 25%.