I offer a useful tidbit for those of you who 1) rely on a page-tagging solution for web analytics, and 2) care about tracking downloads. I've encountered this situation several times as a web analyst, so I thought I'd write up a basic summary of the issue.
You will find this relevant if you are either a newbie web analyst or an experienced web analyst charged with educating your data consumers. Here's what you need to know:
Before you read any further, confirm the method of data collection used on your site. If you've got something other than page-tagging - such as log files, or network collection, or a hybrid solution - then you can stop reading now. The issue I'm about to describe only matters if you use page-tagging alone for data collection.
Measuring downloads initiated is not wrong, but it is slightly upstream from the spot we'd ideally like to track: successful completion of download. Marking this slightly-upstream-but-still-valid action will necessarily inflate the number of real downloads, though, since it’s entirely possible to back out of the process before actually downloading the file 100%.
What it all means
Do not expect accounting-level precision from tag-based download stats. Take the metric at face value, and make sure everyone who uses the data understands how to interpret it. If you find yourself needing to compare tag-based downloads with an overlapping source of business data, I invite you to read my data reconciliation how-to guide post.
When I encountered this issue with downloads most recently (last month, in fact), my client opted to put a statement like the following as a footnote in a widely-distributed report that includes download stats:
"Values in this report approximate the number of successfully completed [Product X] downloads. Since no status is returned to the server when a download completes, it's not possible to get an exact figure. Therefore, we count downloads initiated."
So, armed with education and footnotes, you and your fellow analysts should feel confident using the "download initiated" value as a valid marker of site success.
Here's one of my favorite pieces by early photographer Edweard Muybridge. As progressive snapshots of a single activity, it seems appropriate to include it here.
Image credit, Digital Journalist.