Efficiency / post-view conversion refers to the measurement of how effectively an advertisement or marketing campaign converts viewers into customers after they have been exposed to the initial ad. This metric takes into account the number of people who saw the ad and then took a desired action, such as making a purchase or signing up for a service. A high efficiency / post-view conversion rate indicates that the ad was successful in not only capturing the attention of potential customers, but also in persuading them to take action. This metric is important for businesses to track in order to evaluate the effectiveness of their advertising efforts and make informed decisions about future campaigns.