• by Joe Mandese  @mp_joemandese, May 21, 2015

The U.S. ad marketplace declined 9.9% in April, according to a new dynamic market index of Madison Avenue’s media trading volume. The index, called the U.S. Ad Market Tracker, is a collaboration between MediaPost and Standard Media Index, and is based on actual media dollar volume processed from a pool of agencies representing about 80% of the major agency holding companies. The index -- which stands at a 183 for April, the most recent month for which data is available -- was originally set to a base value of 100 in January 2009, which not so surprisingly proves to be a low-volume trading month according to more than four years of data.

The April index is down from a 203 in March and is off 17.6% from its 12-month high of 222 in December 2014, which also proves to be the highest volume month historically. April is up 18.1% from a 12-month low of 155 in July 2014, consistently the lowest volume for monthly trading.

On a year-over-year basis, which may be the most representative way to look at the index in terms of the ad industry’s most natural patterns, the index rose 1 point from a 182 in April 2014, showing that the ad industry is essentially flat.

The chart accompanying this story is being updated dynamically by SMI as they process and refresh data directly from the agency holding companies participating in the pool, and as such represents the most current view of Madison Avenue’s gross trading behavior.

The major agency holding companies representing Madison Avenue are a subset of a much bigger marketplace, which includes independent, regional and long-tail agencies and direct advertiser spending not processed by Madison Avenue’s majors, but it was calibrated to a highly regarded source of total industry volume and proven to be directionally representative of the total marketplace.

MediaPost will report on the index values monthly alongside SMI’s standard marketplace analysis, which also shows the marketplace is relatively flat overall, but that some subsegments are performing better than others. In particular, the biggest media companies are performing better than the rest of the marketplace.

SMI’s “Top 50,” a composite of the 50 largest companies in trading volume with Madison Avenue, declined at a slower rate in April, year-over-year and vs. its 12-month high.

Index values for the total market, the “SMI 50,” national TV and digital media can be viewed by clicking on their respective tab and mousing over each date.

The U.S. Ad Market Tracker is part of a series of market indexes MediaPost has been developing with the best sources of the most empirical ad market data in order to cover the marketplace more akin to Wall Street’s market coverage. The indexes, like the RTB 500 published on conjunction with Owner IQ, are new, take some getting used to, and are subject to interpretation, analysis and each user’s own meaning, but they are all based on pure market data.

Stay tuned in coming months for more of the same. Please gives us feedback, or weigh in directly via public comments. And use them however you see fit.