When advertisers evaluate media spending, their main concern is the return on their investment. Online advertising is particularly measurable in this regard because immediate responses to an ad can be measured directly from the click to the purchase. However, online advertising is also responsible for driving additional purchases through the branding value of the ad impression itself, and this effect often goes unmeasured. Many online advertisers do not or cannot track the consumer who views an ad but does not immediately respond, and later purchases the product. This type of purchase, is often referred to as a "view-based conversion" or "view-through."