Mediabase

Mediabase is a division of Premiere Radio Networks, located in Sherman Oaks, California. Mediabase is a music industry website containing in-depth charts and analysis based on the monitoring of 1,836 radio stations in the US and Canada, in 175 radio markets, covering 25 radio formats. Mediabase also owns and operates ratethemusic.com, a service that allows consumers to rate music for the radio and record industries.

History
Mediabase was founded in 1985 by Nancy and Rich Deitemeyer. Originally known as Mediascan, the company changed its name to Mediabase in 1987. Mediabase became the industry's first mass-airplay monitoring company in late 1987. Their charts have been featured in USA Today.

Formats

 * Mainstream AC
 * Hot AC
 * Rhythmic AC
 * Adult Hits
 * CHR/Pop
 * CHR/Rhythmic & Dance
 * Urban
 * Urban AC
 * Country
 * Alternative
 * Active Rock
 * Mainstream Rock
 * Classic Rock
 * AAA
 * Smooth Jazz
 * Christian AC
 * Gospel
 * Regional Mexican
 * Spanish Contemporary
 * Tropical Latin

How to Read
4 1 BRITNEY SPEARS Circus 9184 8641 543 59.659

Let's say the chart looks like the above. This is how you would read the numbers. Last week position-This week position-Artist-Title-Spins from this week-Spins from last week-Difference of spins-Audience impression

Spins
Spins refer to the number of times that a song is played on the radio. If you are currently hearing a song in the radio, that is a Spin that would count for the stats of your radio. Usually, here we talk of the accumulated number of spins for the last seven days, so it's a weekly accumulated number.

Bullet
When the "difference of spins" (see above) is positive, then we have a Bullet. In other words, the bullet is the number of new spins that a song gained over the past 7 days (in our example: 543 is the bullet). There is a common mistake to call bullet as difference of spins, but that is not accurate. A song with a difference of -100 is simply "unbulleted".

Audience Impression (AI)
An audience impression is a measure of how large an audience a song reaches, and is usually expressed in millions of people. For example, one play by a New York radio station might be rated as a certain number of million impressions, meaning that this is a reasonable if necessarily inexact estimate of the number of people who heard it.

Recurrents/Purges
A recurrent is a song that has been taken off the chart since it is too old to be charting, but it is still receiving spins. A song goes recurrent after being in the top 40 of the chart for over 20 weeks and is below position number 20.

A purge is when a song has reached the top 40, but has now dipped below the top 40 and doesn't show any sign of ever returning. The song is then taken off the chart to make way for other songs that will probably be more successful to make their way onto the chart.

Adds
When a song goes for adds, basically it means it being "officially" released for stations to add the song. The promo CD is usually sent out a little before or around the adds date as well. Also, just because a station spins a song doesn't mean it's been added, it has to be added to their playlist and spun regularly throughout the week, not just one or two spins here and there. Adds dates don't really affect major artists since their music is bound to take off anyways, but an adds date possibly gives it a little boost, reminding programmers that a song is going for adds that week.