A bumper sticker is an adhesive coated label or sticker with a message printed, intended to be attached to the bumper of a car and to be read by the other vehicles. Most bumper stickers are about 30 cm by 8 cm (12 in by 3 in) and are mostly made of PVC materials. Bumper stickers can be about commercial, religious, secular, humorous, or to support a sports team or other organizations. Bumper stickers may promote or oppose a particular philosophical or political position. In some countries, such as Canada or the United States, bumper stickers are a popular way of showing your support for a political candidate for a government seat. In other countries like UK they are rarely seen. One variety of bumper sticker is the country abbreviations. This is typically used for cars crossing international borders. But in europe now, the country tags are displayed on the license plate itself. In US and Canada, these have turned into tags indicating a country with which the driver affiliates. People who prefer to exhibit their individuality through these bumper stickers may take part in more acts of road rage. Colorado State University social psychologist, William Szlemko, claims that aggressive driving is linked to the number of stickers a person has on his/her car, regardless of the messages portrayed by the stickers.