From a "Why, who cares" perspective website (and app) speed are highly correlated with conversion and engagement.
Google's headline research on the subject says "Improving your load time by 0.1s can boost conversion rates by 8%."
Some add'l data, sourced by Neilsen Group below:
- Google found that increasing the load time of its SERPs by half a second resulted in a 20% higher bounce rate.
- Google found 53% of mobile visits ended if a page took longer than 3 seconds to load.
- Akamai aggregated data from 17 retailers (7 billion pageviews) and found that conversion rates were highest for pages that loaded in less than 2 seconds; longer load times correlated with 50% drops in conversion rates and increased bounce rates, especially for mobile visitors.
- BBC found that for every extra second of page load time, 10% of users will leave.
Want to sell / fix this?
Here's the best three simple resource illustrating objective third party results from increasing site speed:
- https://blog.hubspot.com/marketing/page-load-time-conversion...
- https://wpostats.com/
- https://www.cloudflare.com/learning/performance/more/website...
Here is a more compelling deeper look from a leader in the UX space:
- https://www.nngroup.com/articles/the-need-for-speed/
Here's a really well written article about how to PROVE to the powers that be that site speed is worth testing:
https://web.dev/site-speed-and-business-metrics/