Vanessa Fox. Nude.

The thing about Feedburner subscriber numbers is that Feedburner has to rely on the feed readers to report accurate numbers. If a reader doesn’t report or reports incorrectly, then the whole Feedburner stat is thrown off. In reality, subscriber numbers are even less useful to track than page views (my in-depth review of how Feedburner reports numbers on Search Engine Land explains why reach (the number of people reading your feed each day) is a better indicator of audience engagement than subscribers (for instance, since the total subscriber number includes those who subscribed but never read and those who subscribed on one service, then switched services and subscribed again).

Feedburner could make it easier. They could have handy historical charts for reach like they do for total subscriber numbers. Not that it would do that much good. We would continue to measure subscriptions like we do page views — more is better! Even if it’s not.

That the total Feedburner number is made up of lots of individual services with their own quirks makes measurement difficult as well. I would love to be able to see historical charts by service, to make it easy to pinpoint anomalies within trends. For instance, when Google Reader doesn’t report numbers one day, that’s not obvious from the overall count, but is when you compare subscriber numbers by service by day. But the only way to do that is to click through to each day and look at the pie charts. Or if you’re super geeky, you might manually put all the numbers into a spreadsheet.

Take this week. My total number went from 1279 on Monday to 1450 on Thursday. Just looking at the overall numbers, it looks like my subscriber base was steadily growing:

But then, Friday’s numbers dropped down to 1321.

What happened?

The only way to tell is to dive into each day’s numbers. Compare Monday:

to Tuesday:

Everything looks about the same except that my Netvibes subscribers went from 181 to 305. (This was around the same time they released their newest version in private beta.) This new Netvibes number stayed pretty constant on Wednesday and Thursday, but on Friday, dropped back down to 182.

Who knows what happened. Maybe Netvibes was double counting those users who moved to the new private beta (counting both their old accounts and new accounts)? Maybe upgrading their database just caused a glitch. In any case, it appears that the anomaly has been corrected.

Of course, this same type thing will happen (without correction) anytime a new service opens. People who previously had subscriptions on other services will try the new one, causing double counts. Which is part of why Rick Klau is right about reach being a better indicator of reader engagement. Although my total subscriber count went down yesterday, my reach number was way up (likely thanks to the fact that I actually wrote something for people to read).

Did anyone else notice a bump in subscribers then a subsequent dip this week? Or am I the only obsessed one?