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There are two types of radio audience data: measures of audience size, and everything else. The measures of audience size are estimates which replace the production and sales data for every other industry. The "everything else" category covers questions which only customers can answer - for any industry. These include customer satisfaction, attitudes, and behaviour.
For now, let's focus on measuring the size of audiences. The three main measures of audience are size, reach, and share.
Audience size is the number of people listening to the station. This is not as simple as it seems, because it's not one number: it varies constantly. It doesn't make sense to say "we have an audience of 50,000." There might be 50,000 listeners right now, but maybe 45,000 in half an hour, and 60,000 at the same time tomorrow. A more useful concept is the average audience size for a particular time period. Averaged across 24 hours of the day, the audience will be smaller than when averaged from 6 am to midnight - because most people are asleep between midnight and 6 am.
The most useful measure of audience size is related to time zone averages, such as 6-9am, 9 am to noon, noon to 4 pm, 4 pm to 7 pm, 7 pm to midnight, midnight to 6 am.
But to calculate the average audiences in those time zones, you must first know the audience in smaller periods: usually 15 or 30 minutes. Audience size is not easy to measure: it usually requires listeners to fill in detailed diaries, showing each station they listen to, in each quarter-hour, for a week or so.
Reach is the number of different listeners in a given time zone. The longer the time zone, the more listeners there are. The ultimate reach question is "Have you ever listened to this station in your life?" That question produces a lot more Yes answers than "Did you listen in the last 5 minutes?"
The standard for comparing stations is the weekly reach (also known as weekly audience.) The one-week period is used for three reasons
Reach can be expressed either in thousands of people, or as a percentage of a population. If you add up the weekly reach percentages for all the stations in a market, the total will often be about 200%. This means that the average person listens to 2 stations in a week. Reach is much simpler to measure in a survey than is audience size: reach doesn't require a diary, and small changes to the wording of questions don't cause the reach figures to vary much.
In North America, you sometimes hear the term cumulative audience (abbreviated to cume). This is identical to reach. Another synonym for reach is penetration.
A variation on weekly reach is the regular audience: the number of people who say they "usually listen to this station at least once a week." Though this measure is easily obtained from a survey, it's not as accurate as a weekly reach derived from a question such as "Which stations have you listened to in the last seven days?" because most people think their habits are more regular than is really the case.
Share is more complex. A station's share is the answer to this question: "Of all person-hours spent listening to radio, what percentage of those were to this station?" Share is not a percentage of people, but a percentage of total time. If you add up the shares for all the stations in a market, the total must be 100%.
To put it another way: if, in a week, 27% of people listen to your station, that does not mean your share is 27% - because (a) many people listen to more than one station, and (b) people may spend different amounts of time with each station they listen to.
Measuring share - like measuring audience size - requires a detailed diary. Thus, share is expensive and difficult to measure.
Less common measures derived from audience size surveys include awareness, availability, duration of listening, frequency, impressions, and loyalty.
Availability. Several different definitions of availability are used around the world. The commonest definition relates to the entire radio audience, not to one station. Availability is defined as the number of people available to listen to radio (at a particular time of day, and day of the week). This availability figure includes the number already listening, as well as the number of people who could easily listen to radio, but aren't doing so. The word "easily" is the obvious weak point here: how can it be precisely defined?
The standard definition is that people are considered available to listen to radio if they are
(a) already listening to radio, or
(b) awake, and have a radio nearby that they could switch on if they wanted to, and not doing something that requires their full attention, such as watching TV or video.
Awareness is the percentage of people in the coverage area who know that the station exists. This can be measured in two ways: aided and unaided recall. With aided recall (sometimes called prompted), an awareness question is "Have you ever heard of the following radio stations: X, Y, Z?"
An awareness question using unaided recall (sometimes called spontaneous) is "Please tell me all the radio stations you know which broadcast in this area."
Aided recall produces higher awareness figures than unaided recall - sometimes too high to be true. (If station Z doesn't exist, there are always a few people who say they have heard of it.)
Duration of listening. The amount of time that the average listener spends with the station - per week, per day, or per listening session. The per-day figure is most commonly used. For accuracy, this needs to be derived from a diary survey. If you simply ask people "How much time did you spend listening to radio yesterday?" you find a much smaller range of variation than is revealed by diary data.
Frequency is equivalent to duration, but applies to ads and promos. The average frequency of a message is the average number of times it has been heard (usually by those who heard it at all - i.e. excluding people who didn't hear it at all).
Impressions (or Impacts): the aggregate number of times a message has been heard. So if an advertising campaign has 20,000 impressions, it might mean that 20,000 people heard the ad once, or 10,000 heard it twice - or any other combination for which the audience sizes add to 20,000.
Loyalty. For each listener, the loyalty is the percentage of his or her listening time spent with each station - usually over a period of one week. (It should really over a much longer period, but one week is the limit of most people's patience at filling in a diary.) So a 100% loyal listener is one who listens only to one station (in a week). Somebody who spends 50% of their listening hours with one station is 50% loyal to that station.
Rating. This term is normally used for TV, not radio. It means the percentage of households tuned in to a particular channel - e.g. "Our rating at 9pm was 37%."
Sole listeners. The number of people who listen to your station but no other - usually over one week. Sometimes called (mainly in North America) solus listening. Sole listeners are good bait for attracting large advertisers: if those advertisers want to reach everybody, they only way they can reach your sole listeners is by advertising on your station.
All the above figures are derived from audience size surveys - generally those that estimate radio audiences for every quarter-hour of a week, from respondents who keep diaries for a full week. (If a survey covers only one day of each person's listening, you can't work out from that how many people listen to each station some time during a week.)
Some of the above measures are mathematically related. In particular:
Average audience = Reach × Average duration
Impressions = Reach × Average frequency
For example, if 30,000 people listen to your station for an average of 10 hours a week, that's 300,000 person-hours a week. If you played a promo every quarter-hour, that would be 1.2 million impressions a week for the promo.
The size of its audience is not the only measure of a station's effectiveness. All the above measures are derived from surveys of audience size, but other types of measure are often more important for non-commercial stations. These effectiveness measures include attentiveness, satisfaction, and actions after listening. All of these can be estimated by surveys
Attentiveness is a measure of how much attention listeners are paying to a radio broadcast.
Most diary surveys measure audiences at a very low level of attention - typically, "being in the same room as a radio that is audible." This measure produces large numbers (which impress advertisers) but works in favour of music stations and against news-talk stations.
If the standard diary question is changed from "were you in the room?" to "were you paying full attention?" or "were you concentrating on the radio program?" the diary is now measuring attentiveness. Measures of attentive share and attentive reach can now be derived from that diary.
If your station has a lot of spoken programs, it will probably rank more highly on an attentiveness measure than on the usual "being in the room" diary listening criterion.
If a station wants to keep its listeners, it must satisfy them. With increasing competition between stations, listener satisfaction is becoming an important measure of a station's effectiveness. A change in satisfaction can be an early warning of a change in audience size, because opinions usually change before habits do.
Actions after listening are the ultimate goal of many radio programs. Advertisements succeed not when the audience is large, but when people buy the advertised product - or, in the case of social marketing, change their behaviour in the desired ways. And a station that causes its audience to take some sort of action is a more effective station than one with a passive audience.
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