Continuing the discussion from What are the quantiles of the Pagespeed score for the latest crawl?:

This got me thinking about ACTUAL speed of loading of webpages, and how it is changing over time. I modified Ilya’s query from the previous post to look at trends in visualComplete, onLoad and SpeedIndex. The numbers are all similar, so I’ll just run my analysis with the SpeedIndex numbers. As you know, SpeedIndex is a WebPageTest measurement of how quickly the screen paints (perceived load time). The faster you paint the whole screen, the lower the score.

So, copying Ilya’s code from the last post, and substituting in SpeedIndex, we can see how perceived page load time has changed over time.

```
SELECT date,
NTH(10, quantiles(SpeedIndex)) tenth,
NTH(20, quantiles(SpeedIndex)) twentieth,
NTH(30, quantiles(SpeedIndex)) thirtieth,
NTH(40, quantiles(SpeedIndex)) fortieth,
NTH(50, quantiles(SpeedIndex)) fiftieth,
NTH(60, quantiles(SpeedIndex)) sixtieth,
NTH(70, quantiles(SpeedIndex)) seventieth,
NTH(80, quantiles(SpeedIndex)) eightieth,
NTH(90, quantiles(SpeedIndex)) ninetieth
FROM (
SELECT
STRFTIME_UTC_USEC(INTEGER(createDate*1000000), "%Y-%m") date, SpeedIndex
FROM httparchive:runs.2013_04_01_pages_mobile,httparchive:runs.2013_05_01_pages_mobile,httparchive:runs.2013_06_01_pages_mobile,httparchive:runs.2013_07_01_pages_mobile,httparchive:runs.2013_08_01_pages_mobile,httparchive:runs.2013_09_01_pages_mobile,httparchive:runs.2013_10_01_pages_mobile, httparchive:runs.2013_11_01_pages_mobile
)
GROUP BY date, order by date
```

You may notice that the data is only for the last 7 months. In March, the default speed for HTTP Archive was changed from 1.5 MBPS to 5.0 MBPS. This obviously skews the load times, and so the older data was omitted.

Remember that here, the LOWER percentiles are the faster sites, and the higher percentiles are the slower sites.

In the last 7 months, there is a slow upward growth to these lines. This implies that all sites are getting SLOWER over time. If we assume that the growth is linear (the lines are not really great linear fits, but with only 7 data points, it seems an ok assumption), we can get the slope of these lines:

The fastest sites are (on average) getting 23 ms slower a month, and the slowest sites are adding nearly 90 ms every month. That is not totally unexpected. However, I will save the scariest piece of data for last. While it appears that the faster sites are slowly getting slower, if you look at the increase as a percentage of load time:

The faster sites are (as a percentage of load time) gettting slower faster than the big bloated sites.

NOTE: I attempted the same for mobile, but the mobile “speed” was changed in July, and there is a lot of noise - there are 2 months with over 100% jump in the data. It will be a while until the data settles down to perform this same analysis on mobile.