You need to know the actual number of copies of a newspaper or magazine that are distributed. Unfortunately print publications have a sad history of lying about their distribution. Today they also tend to use “readership” numbers, assuming a certain number of readers per each copy of the newspaper or magazine. That number is pretty much a wild guess.
You’re not likely to find the LA Times and LA Weekly lying about their circulation. Both of them are “audited” by reputable and independent third parties such as the Alliance for Audited Media (the AAM, formerly the Audit Bureau of Circulation) that actually check on their distribution and report the numbers. You should ask for a copy of an audit from any print publication in which you want to advertise. If the publication doesn’t have an audit (and some small ones don’t because audits are expensive), ask for a copy of its printer’s statement, which says how many copies are printed. If the publication won’t provide either, you don’t want to advertise in it.
The AAM not only count the number of copies a major publication such as the LA Times distributes, it also counts how many are actually purchased from newsracks and newsstands as well as delivered to subscribers. (Of course they can’t guarantee that the subscribers read the newspaper or magazine they pay for, or that they see your ad. That’s a major disadvantage for print publications competing with websites, which can track that).
Many free publications such as the Independent weekly and Frontiers magazine don’t provide audits of the number of copies actually picked up. Left over copies typically are picked up and trashed or recycled by the publication’s distributor when the latest issue is put on the street. Sometimes you’ll find bundles of copies from several different issues left behind. That means someone is paying for an ad that no one is seeing
