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<script type="text/javascript">
/* gms.scrolltracking.js | v0.2
   www.gandke.de
   Copyright (c) 2015 Markus Baersch (@mbaersch)
   Licensed under MIT license.
*/
var trackBottomScroll = 0;
var trackScrollStep = 20 ;
var useDataLayer = true ;  
window.onscroll = function () {
var docHeight = Math.max(document.body.scrollHeight, document.documentElement.scrollHeight,
                         document.body.offsetHeight, document.documentElement.offsetHeight,
                         document.body.clientHeight, document.documentElement.clientHeight);
if (trackBottomScroll < 100 && ((document.documentElement.scrollTop||document.body.scrollTop) >= 
   (docHeight - window.innerHeight) / 100 * (trackBottomScroll+trackScrollStep)))
try {
  trackBottomScroll += trackScrollStep;
  if (useDataLayer)
    dataLayer.push({'scrollPercentage': trackBottomScroll, 'event': 'updScrollPercentage'});
  else
    ga('send', 'event', 'Interaction', 'ScrollPercentage', trackBottomScroll.toString());
    
} catch(e) {} 
} ;
</script>