In Podcasting Metrics Series Part 2, I pointed out the problem with looking at the # of hits to a file for estimating the # of downloads. A single download can result in many hits. The hits stat will always be bigger than the actual number of downloads.
So how can we get a more accurate idea of the number of downloads? Services that offer podcast metrics (e.g. Libsyn, Podpress, Feedburner, Podtrac, RadioTail Ripple etc.) track things such as the IP address of each request to a file to determine how many unique users have downloaded (or at least attempted to download) the podcast file. This leads to a more accurate, although still imperfect, measurement.
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