A saying attributed to the famous Philadelphia retailer John Wanamaker is that, “Half the money I spend on advertising is wasted; the trouble is I don't know which half.” Apparently, that saying can be updated for the Internet age to read, “Half the traffic to my website is non-human; the trouble is I don't know which half.”

In fact, the percentage is worse than that. According to a study by online researcher Imperva, a whopping 61.5% of traffic on the web is non-human. What do we mean by non-human? Well, it’s a category that include search engines, software that’s scraping your website, hackers, spammers and others who are up to no good.

And yes, it gets worse. The lower the traffic to your website, the greater the percentage that is likely to be non-human. Indeed, if your site gets 1,000 of fewer visits per day, the study suggests that as much as 80% of your traffic may be non-human.

Sure, a lot of this non-human traffic is search engines (and you’d be amazed how many there still are out there), and that’s probably a good thing. After all, we want exposure. But the rest of this traffic is more dubious. About 5% of your overall site traffic is likely to be scrapers -- –people using software to grab all the content on your site, for purposes benign or evil. Sure, they can’t get to your password protected content, but if you publish any amount of free data on your site in structured form, chances are that others now have that data in their databases.

Obviously, if your sell online advertising, these statistics represent an inconvenient truth. The only saving grace is that your competitors are in the same boat. But if you are a subscription site, does any of this even matter?

I think it does. Because all this non-human activity distorts all of our web analytics in addition to our overall visitor counts. Half the numbers we see are not real. These non-human visitors could lead you to believe certain pages are more popular on your site than the really are; this could cause you to use bad insights to fashion your marketing strategy. And if you are using paid search to generate traffic, you could be getting similarly bad marketing data, and paying for the privilege as well.

Most importantly, this non-human traffic distorts reality. If you’re beating yourself up because of low response, lead generation or order rates, especially given the number of uniques and page views you appear to be getting, start by dividing by two. Do your numbers suddenly look a lot better? Bots and scrapers and search engines don’t request demos, don’t download white pages and certainly don’t buy merchandise. Keep that in mind next time you’re looking at your site analytics reports or puzzling why some pages on your site get so much more attention than others. Remember, not all data are good data.