How Much Data Is Missing from Analytics? And Other Analytics Black Holes

How Much Data Is Missing from Analytics? And Other Analytics Black Holes

In this post, I’ll explain why data is missing from your web analytics platforms and how large the impact could be. Side note: Our test setup (multiple trackers & customized GA) On Distilled.net, we have a standard Google Analytics property running from an HTML tag in GTM (Google Tag Manager). Two of these extra implementations — one in Google Tag Manager and one on page — run locally hosted, renamed copies of the Google Analytics JavaScript file (e.g. www.distilled.net/static/js/au3.js, instead of www.google-analytics.com/analytics.js) to make them harder to spot for ad blockers. Effect of ad blockers Some ad blockers block web analytics platforms by default, others can be configured to do so. Lost data due to ad blockers: ~10% Ad blocker usage can be in the 15–25% range depending on region, but many of these installs will be default setups of AdBlock Plus, which as we’ve seen above, does not block tracking. Lost data due to filters: ??? Reason 4: GTM vs. on-page vs. misplaced on-page Google Tag Manager has become an increasingly popular way of implementing analytics in recent years, due to its increased flexibility and the ease of making changes. Effect of GTM and misplaced on-page code Traffic as a percentage of baseline (standard Google Tag Manager implementation): Google Tag Manager Modified & Google Tag Manager On-Page Code In Modified & On-Page Code In On-Page Code Misplaced In Chrome 100.00% 98.75% 100.77% 99.80% 94.75% Safari 100.00% 99.42% 100.55% 102.08% 82.69% Firefox 100.00% 99.71% 101.16% 101.45% 90.68% Internet Explorer 100.00% 80.06% 112.31% 113.37% 77.18% There are a few main takeaways here: On-page code generally reports more traffic than GTM Modified code is generally within a margin of error, apart from modified GTM code on Internet Explorer (see note below) Misplaced analytics code will cost you up to a third of your traffic vs. properly implemented on-page code, depending on browser (!) Lost data due to GTM: 1–5% Google Tag Manager seems to cost you a varying amount depending on what make-up of browsers and devices use your site. Lost data due to misplaced on-page code: ~10% On Teflsearch.com, the impact of misplaced on-page code was around 7.5%, vs Google Tag Manager.

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If you’ve ever compared two analytics implementations on the same site, or compared your analytics with what your business is reporting in sales, you’ve probably noticed that things don’t always match up. In this post, I’ll explain why data is missing from your web analytics platforms and how large the impact could be. Some of the issues I cover are actually quite easily addressed, and have a decent impact on traffic — there’s never been an easier way to hit your quarterly targets. 😉

I’m going to focus on GA (Google Analytics), as it’s the most commonly used provider, but most on-page analytics platforms have the same issues. Platforms that rely on server logs do avoid some issues but are fairly rare, so I won’t cover them in any depth.

Side note: Our test setup (multiple trackers & customized GA)

On Distilled.net, we have a standard Google Analytics property running from an HTML tag in GTM (Google Tag Manager). In addition, for the last two years, I’ve been running three extra concurrent Google Analytics implementations, designed to measure discrepancies between different configurations.

(If you’re just interested in my findings, you can skip this section, but if you want to hear more about the methodology, continue reading. Similarly, don’t worry if you don’t understand some of the detail here — the results are easier to follow.)

Two of these extra implementations — one in Google Tag Manager and one on page — run locally hosted, renamed copies of the Google Analytics JavaScript file (e.g. www.distilled.net/static/js/au3.js, instead of www.google-analytics.com/analytics.js) to make them harder to spot for ad blockers. I also used renamed JavaScript functions (“tcap” and “Buffoon,” rather than the standard “ga”) and renamed trackers (“FredTheUnblockable” and “AlbertTheImmutable”) to avoid having duplicate trackers (which can often cause issues).

This was originally inspired by 2016-era best practice on how to get your Google Analytics setup past ad blockers. I can’t find the original article now, but you can see a very similar one from 2017 here.

Lastly, we have (“DianaTheIndefatigable”), which just has a renamed tracker, but uses the standard code otherwise and is implemented on-page. This is to complete the set of all combinations of modified and unmodified GTM and on-page trackers.

Two of Distilled’s modified on-page trackers, as seen on https://www.distilled.net/

Overall, this table summarizes our setups:

Tracker

Renamed function?

GTM or on-page?

Locally hosted JavaScript file?

Default

No

GTM HTML tag

No

FredTheUnblockable

Yes – “tcap”

GTM HTML tag

Yes

AlbertTheImmutable

Yes – “buffoon”

On page

Yes

DianaTheIndefatigable

No

On page

No

I tested their functionality in various browser/ad-block environments by watching for the pageviews appearing in browser developer tools:

Reason 1: Ad Blockers

Ad blockers, primarily as browser extensions, have been growing in popularity for some time now. Primarily this has been to do with users looking for better performance and UX on ad-laden sites, but in recent years an increased emphasis on privacy has also crept in, hence the possibility of analytics blocking.

Effect of ad blockers

Some ad blockers block web analytics platforms by default, others can be configured to do so. I tested Distilled’s site with Adblock Plus and uBlock Origin, two of the most popular ad-blocking desktop browser addons, but it’s worth noting that ad blockers are increasingly prevalent on smartphones, too.

Here’s how Distilled’s setups fared:

(All numbers shown are from April 2018)

Setup

Vs. Adblock

Vs. Adblock with “EasyPrivacy” enabled

Vs. uBlock Origin

GTM

Pass

Fail

Fail

On page

Pass

Fail

Fail

GTM + renamed script & function

Pass

Fail

Fail

On page + renamed script & function

Pass

Fail

Fail

Seems like those tweaked setups didn’t do much!

Lost data due to ad blockers: ~10%

Ad blocker usage can be in the 15–25% range depending on region, but many of these installs will be default setups of AdBlock Plus, which as we’ve seen above, does not block tracking. Estimates of AdBlock Plus’s market share among ad blockers vary from 50–70%, with more recent reports tending more towards the former. So, if we assume that at most 50% of installed ad blockers block analytics, that leaves your exposure at around 10%.

Reason 2: Browser “do not track”

This is another privacy motivated feature, this time of browsers themselves. You can enable it in the…

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