The “performance poverty line”: What is it and why does it matter?

Depending on whom you ask, the ideal page load can be 100 milliseconds, 400 milliseconds, 2 seconds… you get the picture.

In our industry, we talk a lot about big, hairy, audacious performance goals, but what about the other end of the spectrum: the performance poverty line?

The performance poverty line is the plateau at which load time ceases to matter because you’ve hit close to rock bottom in terms of business metrics. If your pages are below the performance poverty line, making them a couple of seconds faster doesn’t help your business.

But what is the performance poverty line? Is it quantifiable? Does it vary from business metric to business metric? Is it widely applicable? I went looking for it. It ended up being pretty easy to find.

Methodology

A couple of years ago, I presented a session at Velocity in which I talked about the impact of poor performance on some of the usual business metrics: conversions, bounce rate, and page views per visit. In that presentation, I showed a set of graphs that aggregated user data — millions of transactions recorded in Stangeloop’s monstrously huge analytics database — from five of our ecommerce customers.

To find out the current performance poverty line, I simply revisited these five sites, gathered data from millions of recent transactions, then plotted it on a set of graphs. For the sake of comparison, I also included the 2010 data. It makes for an interesting set of snapshots:

Performance poverty line: bounce rate

Performance poverty line: pages per visit

Performance poverty line: conversion rate

Observation #1: The performance poverty rate is around 8 seconds.

For these five sites, metrics more or less bottom out at around 8 seconds. What’s noteworthy here isn’t just this number, but how incredibly consistent it is across all three metrics.

Observation #2: When pages are slow, business metrics suffer more today than they did two years ago.

This doesn’t apply just to the 8-second mark — it’s consistent at every page speed. For example, look at the final graph. A page that took 6 seconds to load in 2010 suffered a -40% conversion hit. Today, a 6-second page takes a -50% hit. Or look at the second graph, where you see that a relatively fast 4-second page suffers a -30% hit in page views per visit in 2010, but in 2012 a 4-second page takes more than a -40% hit. This indicates a huge change in consumer expectations. Simply put, users are less willing than ever to suffer slow pages.

Takeaway: Try this with your own data.

There’s no point in killing yourself to take your pages from 16 seconds to 8 seconds if you don’t budge your key business metrics. I invite you to determine your site’s performance poverty line with your own data, assuming you have enough data with which to perform statistically relevant analysis. The performance poverty line for your site might be slightly different than for the sites I tested, depending on your content and your audience. Once you’ve identified your poverty line, you’ll know your lowest bar for performance.

When you do determine your site’s poverty line, I’d love to know if it’s close to my results or radically different. Drop me a line and let me know.

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6 thoughts on “The “performance poverty line”: What is it and why does it matter?

  1. Interesting stats. One quick question is the bounce defined as visits with one pageview? If so would be interesting to see what the #exits to Exit Page correlation is?

    Often people will browser 1+ pages to leave in frustration after a couple of reloads or retries. Bounce rate does not take in account these cases.

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