In marketing, Target Rating Points are a subdivision of the Gross Rating Points. TRP measures the percentage of viewers or listeners or readers that are considered to be interested or "in the market" for a particular good or service. In other words, a Gross Rating point would be the total number of viewers of an advertisement while the Target Rating Point would be the viewers that would actually take interest and consider a purchase of the product being advertised. Both the GRP and the TRP are critical elements in determining the marketing effectiveness of a particular advertisement.
Target Ratings Points are an educated estimate of the Gross Ratings Points. Gross Ratings points are defined as the sum of ratings achieved by a particular media. They measure the total volume of conveyance of an advertiser's message to the audience. The formula is GRP = 100 times reach times frequency. Frequency is defined as the number of times an average person or household is exposed to the advertising schedule. Reach is defined as the exclusive target audience divided by the total audience. This simple calculation is known as the reach times frequency formula. If an advertising campaign delivers a message 5 times to a population of 1,000,000 and there are 100,000 unique viewers then: 5 x (100,000/1000, 000) x 100 = 50.
Another example would be to imagine 100 drivers listening to the radio during their daily commute. Each car would represent 1% of the total radios turned on therefore each car would represent a 1 rating each time the radio commercial airs when the radio in that car is on. If the advertisement aired a total of five times during each commute each car could possibly count as five Gross Rating points.
Target rating points now, are a function of the gross rating point and can be represented as a percentage of the GRP. Suppose an advertiser is selling an item aimed at men between 50 and 60 years of age. Demographics may show for example that of our 100 homes, 50 are occupied by men between the ages of 50 and 60. That would make our target rating points 50% of the GRP (in this case, 25.) This of course is a very simplistic example and a more in depth demographic study would be needed to determine the television habits of the 50 to 60 year old male age group but hopefully one can see how Total Ratings Points are determined when analyzing a marketing campaign.