What’s the performance “sweet spot” — defined as the page load time that yields the peak conversion rate — for any given site?
It’s a fascinating question because there’s no single answer. The sweet spot can change from day to day (or even from time of day to time of day), from region to region, and from site to site.
Over the past few months, I’ve gone down a research rabbit hole, chasing this elusive metric. The back-to-school shopping season presented a great opportunity to explore a cohort of similar sites and see what trends emerge.
I wanted to see what impact, if any, changes in load time had on retail business metrics — not just for this year but for 2014 as well. I decided to dig into our wealth of real-user data and ask it a few questions:
- What was the peak conversion rate for each year? What changes, if any, happened between 2014 and 2015?
- What load time correlated to peak conversions each year? Again, what differences are noticeable from year to year?
- How much traffic came from each device type each year?
For this research, we loaded beacon data (via our mPulse performance monitoring solution) for twelve different IR200 retailers, all of which cater to the back-to-school shopping crowd. We focused on the one-month period leading up to Labor Day for 2014 and 2015. (That would be August 1 – September 1, 2014 and August 7 – September 7, 2015.)
All together, this totalled more than 500 million user sessions, resulting in 6.5 billion beacons. The findings below are based on this aggregated data.
Finding 1: Smartphones dominate retail traffic, doubling in just one year
We all know that when it comes to mobile, change happens fast, but I have to confess that even I was a bit floored by this. Check out the transposition of desktop (blue) and smartphone (green) traffic in the graph below. In 2014, just over 60% of total traffic came from desktop users, while around 33% came from smartphones. Just one year later — for the same set of sites — 65% of traffic came from smartphones, while 25% came from desktop.
Tablet traffic (orange) also grew — from almost 6% to almost 10% — which is significant, but not as phenomenally so as the numbers for smartphone shopping.
Finding 2: Peak conversion rate for smartphones increased by 450%
Shoppers aren’t just using mobile more, they’re also converting at a much higher rate this year than last year. In 2014, the peak conversion rate for this set of sites was a mere 0.4% — not awesome. Just twelve months later, peak conversion rate for the same set of sites was just over 2.2%. In other words, between 2014 and 2015, the peak conversion rate grew by 450%.
The graphs below illustrate this huge shift. The gold bars represent the distribution of sessions across load times from 1 to 15 seconds. The blue line represents the conversion rate across these sessions.
Finding 3: The performance “sweet spot” shifted from 6 seconds to 2 seconds for smartphone users
In 2014, the performance sweet spot (again: the page load time that yields the best conversion rate) was around 6 seconds. In 2015, the sweet spot was much earlier — just over 2 seconds.
This shift may represent a new trend in user expectations: mobile users expect pages to load faster. But looking at the distribution of traffic, I think it’s also important to commend these site owners for being able to deliver dramatically faster pages to their visitors. In 2014, most pages took 5 or 6 seconds to load. In 2015, most loaded in 2 or 3 seconds — pretty impressive.
Finding 4: The performance “sweet spot” for desktop moved from 3 seconds to 2 seconds
Online retail was pretty healthy in August, rising 2.6% over August 2014. So it’s not surprising that the retailers we studied also experienced an increase in average peak conversion rate — from 1.3% in 2014 to almost 1.8% in 2015. Also unsurprising is the shift in the sweet spot for desktop: peak conversion rate happened at 2 seconds in 2015 compared to 3 seconds in 2014.
Unfortunately, you can see that the bulk of converted traffic — represented by the yellow bars — received pages that were slower than that. In an ideal world, those yellow bars would fit snugly underneath that blue line.
Finding 5: In 2015, the “performance poverty line” happens much earlier for both desktop and mobile
We define the “performance poverty line” as the point at which conversion rates dip down and plateau after the performance peak. In 2014, conversion rates declined slowly after their peak, for both mobile and desktop. In 2015, conversions take a sharp downturn after they peak. For both device types, the poverty line begins at 4 seconds and establishes itself at 6 seconds.
According to a Harris poll of more than two thousand parents, these are the top user experience frustrations parents reported about shopping online for back-to-school items:
While it’s not a shock that security tops the list, load times and crashes are close behind. Our look into the real user data of twelve leading retailers suggests a strong correlation between load times and conversion rate — simply put, faster pages outperform slower pages. Our research also suggests that user expectations are constantly evolving, which means sites must constantly evolve in order to keep up. It’ll be interesting to take another look at these numbers in 2016.
[photo: Brian J. Matis, CC]
- Case study: Mobile pages that are 1 second faster experience up to 27% increase in conversion rate
- Mother’s Day online: Making your pages one second faster could increase conversions by more than 9%
- Performance Monitoring 101: A beginner’s guide to understanding synthetic and real user monitoring
About the Author
Tammy has spent the past two decades obsessed with the many factors that go into creating the best possible user experience. As senior researcher and evangelist at SOASTA, she explores the intersection between web performance, UX, and business metrics. Tammy is a frequent speaker at events including IRCE, Shop.org Summit, Velocity, and Smashing Conference. She is the author of 'Time Is Money: The Business Value of Web Performance' (O'Reilly, 2016).