Google Analytics and Whos.amung.us in realtime visitors, why such an enormous discrepancy?

Question

Since years I use in a site both Google Analytics and Whos.amung.us, both Google analytics and whos.amung.us javascripts are inserted in the same pages in the tracked part of the site.

In real-time visitors, why such an enormous discrepancy ? for example at the moment, Google analytics gives me 9 visitors, whos.amung.us indicates 59, a ratio of 6 times?

Why whos.amung.us is 6 times optimistic than Google Analytics in terms of the realtime visitors?

Google whos.amung.us

My question is:

1. More accurate is GA (smaller number), WAU (greater)?
2. whos.amung.us does not detect robots while Google does?
3. GA ignores visitors from some countries, not whos.amung.us?
4. Some robots/bots execute whos.amung.us javascript for tracking?
5. While no robots/bots can execute the tracking javascript provided by Google Analytics?

To facilitate your analysis, I copy JS code used below:

Google analytics:

<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'MyGaAccountNo']);
_gaq.push(['_trackPageview']);

(function() {
  var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
  ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
  var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
</script>

Whos.amung.us:

<script>var _wau = _wau || []; _wau.push(["tab", "MyWAUAccountNo", "c6x", "right-upper"]);(function() { var s=document.createElement("script"); s.async=true;     s.src="http://widgets.amung.us/tab.js";document.getElementsByTagName("head")[0].appendChild(s);})();</script>

I've aleady signaled this to WAU staff some time ago, NR, I've not done this to Google as they don't handle this kind of feedback. Thank you for your explanations.

Answer 1

The difference is likely to be in the amount of time a visitor is assumed to be on the site after they view a page. For Google Analytics, the default is 30 minutes. I can't find documentation on on the WAU site about he assumptions they are making, but they may be measuring the number of visitors in the past hour or few hours.

Google Analytics also has some trouble with accuracy. If I leave realtime open for 30 minutes, the number of visitors reported using the site doubles. Here is a screenshot that demonstrates this problem. I opened realtime four minutes ago and you can see that the number of visitors per minute is double while I have it open compared to before I had it open.

Answer 2

Googlebot doesn't scrape JavaScript content and Google Analytics source code must be at every page in the website. If it's not, the statistics will show partial information.