Your most impactful Web Vital

Google is about to begin using Core Web Vitals as a ranking factor. So here’s a friendly reminder for everyone that network payload a.k.a. page weight a.k.a. page size is the most impactful metric on your Lighthouse report – even if it’s not deemed a Core Web Vital by Google.

Because of page size, a child in the U.S. – or anywhere – may have to choose between eating lunch or doing homework. Here is why…

Page size and cost

Graph of the cost of site visit based on data from the ITU and World Bank. The cost of data is standardised based on the PPP factor. Prices were collected from the operator with the largest marketshare in the country, using the least expensive plan with a (minimum) data allowance of 500 MB over (a minimum of) 30 days. Prices include taxes. Because these numbers are based on the least expensive plan, they are best case scenarios. Top five most expensive countries: U.S. $0.20, Switzerland $0.18, Ireland $0.17, Canada $.0.12. Further down: Botswana $0.07, Angola $0.05, Tanzania $0.01.
Cost of visiting an average web page worth 2.4MB in 2020
Image source: whatdoesmysitecost.com

The median website weighed 2.4MB in 2020. This translates into 20 cents per page load on a cheap U.S. pre-paid plan. Cheap – that’s a best case scenario.

By the way, does it surprise you that countries like the United States, Switzerland, Ireland, or Canada lead the cost graph above?

Switch to the Cost as % of GNI tab and it almost literally flips over.

Relative cost of site visit based on data from the ITU and World Bank. The cost of data is standardised based on the PPP factor. The cost then has affordability factored in by comparing to the GNI per capita (broken down to a daily number). Prices were collected from the operator with the largest marketshare in the country, using the least expensive plan with a (minimum) data allowance of 500 MB over (a minimum of) 30 days. Prices include taxes. Because these numbers are based on the least expensive plan, they are best case scenarios. Top 5 most expensive: Vanuatu 1.39%, Mauritania 1.31%, Madagascar 1.1%, Niger 0.78%, Tanzania 0.43%. Further down: Ireland 0.14%, United States 0.13%, Canada 0.09%, Switzerland 0.07%.
Same as above, broken down to % of GNI (PPP) per capita
Image source: whatdoesmysitecost.com

Those 20 cents per page equate to 0.13% of a person’s daily income in the U.S. and now appear way further down the list. Check out the other countries, too.

Core Web Vitals vs real life

In Mauritania (at the top of the graph above) a person would pay the equivalent of €2 in purchasing power compared to a person in Germany, or $2.3 in the United States, just to open one (1) page on an average website.

Largest Contentful Paint (LCP): measures loading performance. To provide a good user experience, LCP should occur within 2.5 seconds of when the page first starts loading. First Input Delay (FID): measures interactivity. To provide a good user experience, pages should have a FID of less than 100 milliseconds. Cumulative Layout Shift (CLS): measures visual stability. To provide a good user experience, pages should maintain a CLS of less than 0.1.
Core Web Vitals according to Google

If you’re in Mauritania and you make $15 a day, I wonder how vital a Google-pleasing LCP below 2.5 seconds may feel compared to the fact the same page is burning roughly $1 per second of load time? Writing this article would have cost me more than a week’s income.

Lunch, or homework

Now, back to that child in the U.S. and their homework. 0.13% of a person’s daily income per page view may sound little until you put it into perspective (which is what I learned you’re supposed to do with numbers, otherwise they’re useless). So let’s look at how much folks in the U.S. spend for, say, groceries.

A household with children under 18 in the United States spent approximately 160.35 U.S. dollars per week for groceries in 2020.
Image source: Statista

Weekly grocery expenses of a U.S. household with children under 18 averaged $160 in 2020.

That’s about $23 per day to feed a family.

For sake of example, let’s assume a household of three, including one child under 18, who eat three meals a day. Let’s also ignore price differences in those meals as well as differences in individual eating habits:

$23 daily grocery expenses 
÷ 3 humans
÷ 3 meals
= $2.55/person/meal/day

So on average, a child on a pre-paid plan in the U.S. can eat lunch, or spend the equal amount of money visiting 12 web pages to do their homework.

And there you have it: page size – not a Core Web Vital according to Google, but still your most impactful and, dare I say it, empathetic web performance metric.

Page weight and carbon

Note that I haven’t even dipped into environmental cost. Clearly, other factors, like servers powered by renewable energy, have a much bigger impact on carbon emissions initially. But once you start comparing equally “green” infrastructure, megabytes sent over the wire by a web page start to matter again.

According to Website Carbon Calculator, the average web page tested on their site “produces 1.76 grams CO2 per page view. For a website with 10,000 monthly page views, that’s 211 kg CO2 per year”.

For your perspective, four of those websites equal the yearly CO2 emissions of one Mauritanian. And that’s another post for another time…

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