To keep this post manageable in length, I have only included a small subset of the illustrative examples and discussion. I have published a longer version of this post, with more examples (but the same intro and concluding section), on my personal site.

Last year, during the months of June and July, as my work for MIRI was wrapping up and I hadn't started my full-time job, I worked on the Wikipedia Views website, aimed at easier tabulation of the pageviews for multiple Wikipedia pages over several months and years. It relies on a statistics tool called stats.grok.se, created by Domas Mituzas, and maintained by Henrik.

One of the interesting things I noted as I tabulated pageviews for many different pages was that the pageview counts for many already popular pages were in decline. Pages of various kinds peaked at different historical points. For instance, colors have been in decline since early 2013. The world's most populous countries have been in decline since as far back as 2010!

Defining the problem

The first thing to be clear about is what these pageviews count and what they don't. The pageview measures are taken from stats.grok.se, which in turn uses the pagecounts-raw dump provided hourly by the Wikimedia Foundation's Analytics team, which in turn is obtained by processing raw user activity logs. The pagecounts-raw measure is flawed in two ways:

It only counts pageviews on the main Wikipedia website and not pageviews on the mobile Wikipedia website or through Wikipedia Zero (a pared down version of the mobile site that some carriers offer at zero bandwidth costs to their customers, particularly in developing countries). To remedy these problems, a new dump called pagecounts-all-sites was introduced in September 2014. We simply don't have data for views of mobile domains or of Wikipedia Zero at the level of individual pages for before then. Moreover, stats.grok.se still uses pagecounts-raw (this was pointed to me in a mailing list message after I circulated an early version of the post).
The pageview count includes views by bots. The official estimate is that about 15% of pageviews are due to bots. However, the percentage is likely higher for pages with fewer overall pageviews, because bots have a minimum crawling frequency. So every page might have at least 3 bot crawls a day, resulting in a minimum of 90 bot pageviews even if there are only a handful of human pageviews.

Therefore, the trends I discuss will refer to trends in total pageviews for the main Wikipedia website, including page requests by bots, but excluding visits to mobile domains. Note that visits from mobile devices to the main site will be included, but mobile devices are by default redirected to the mobile site.

How reliable are the metrics?

As noted above, the metrics are unreliable because of the bot problem and the issue of counting only non-mobile traffic. German Wikipedia user Atlasowa left a message on my talk page pointing me to an email thread suggesting that about 40% of pageviews may be bot-related, and discussing some interesting examples.

Relationship with the overall numbers

I'll show that for many pages of interest, the number of pageviews as measured above (non-mobile) has declined recently, with a clear decline from 2013 to 2014. What about the total?

We have overall numbers for non-mobile, mobile, and combined. The combined number has largely held steady, whereas the non-mobile number has declined and the mobile number has risen.

What we'll find is that the decline for most pages that have been around for a while is even sharper than the overall decline. One reason overall pageviews haven't declined so fast is the creation of new pages. To give an idea, non-mobile traffic dropped by about 1/3 from January 2013 to December 2014, but for many leading categories of pages, traffic dropped by about 1/2-2/3.

Why is this important? First reason: better context for understanding trends for individual pages

People's behavior on Wikipedia is a barometer of what they're interested in learning about. An analysis of trends in the views of pages can provide an important window into how people's curiosity, and the way they satisfy this curiosity, is evolving. To take an example, some people have proposed using Wikipedia pageview trends to predict flu outbreaks. I myself have tried to use relative Wikipedia pageview counts to gauge changing interests in many topics, ranging from visa categories to technology companies.

My initial interest in pageview numbers arose because I wanted to track my own influence as a Wikipedia content creator. In fact, that was my original motivation with creating Wikipedia Views. (You can see more information about my Wikipedia content contributions on my site page about Wikipedia).

Now, when doing this sort of analysis for individual pages, one needs to account for, and control for, overall trends in the views of Wikipedia pages that are occurring for reasons other than a change in people's intrinsic interest in the subject. Otherwise, we might falsely conclude from a pageview count decline that a topic is falling in popularity, whereas what's really happening is an overall decline in the use of (the non-mobile version of) Wikipedia to satisfy one's curiosity about the topic.

Why is this important? Second reason: a better understanding of the overall size and growth of the Internet.

Wikipedia has been relatively mature and has had the top spot as an information source for at least the last six years. Moreover, unlike almost all other top websites, Wikipedia doesn't try hard to market or optimize itself, so trends in it reflect a relatively untarnished view of how the Internet and the World Wide Web as a whole are growing, independent of deliberate efforts to manipulate and doctor metrics.

The case of colors

Let's look at Wikipedia pages on some of the most viewed colors (I've removed the 2015 and 2007 columns because we don't have the entirety of these years). Colors are interesting because the degree of human interest in colors in general, and in individual colors, is unlikely to change much in response to news or current events. So one would at least a priori expect colors to offer a perspective into Wikipedia trends with fewer external complicating factors. If we see a clear decline here, then that's strong evidence in favor of a genuine decline.

I've restricted attention to a small subset of the colors, that includes the most common ones but isn't comprehensive. But it should be enough to get a sense of the trends. And you can add in your own colors and check that the trends hold up.

Page name	Pageviews in year 2014	Pageviews in year 2013	Pageviews in year 2012	Pageviews in year 2011	Pageviews in year 2010	Pageviews in year 2009	Pageviews in year 2008	Total	Percentage	Tags
Black	431K	1.5M	1.3M	778K	900K	1M	958K	6.9M	16.1	Colors
Blue	710K	1.3M	1M	987K	1.2M	1.2M	1.1M	7.6M	17.8	Colors
Brown	192K	284K	318K	292K	308K	300K	277K	2M	4.6	Colors
Green	422K	844K	779K	707K	882K	885K	733K	5.3M	12.3	Colors
Orange	133K	181K	251K	259K	275K	313K	318K	1.7M	4	Colors
Purple	524K	906K	847K	895K	865K	841K	592K	5.5M	12.8	Colors
Red	568K	797K	912K	1M	1.1M	873K	938K	6.2M	14.6	Colors
Violet	56K	96K	75K	77K	69K	71K	65K	509K	1.2	Colors
White	301K	795K	615K	545K	788K	575K	581K	4.2M	9.8	Colors
Yellow	304K	424K	453K	433K	452K	427K	398K	2.9M	6.8	Colors
Total	3.6M	7.1M	6.6M	6M	6.9M	6.5M	6M	43M	100	--
Percentage	8.5	16.7	15.4	14	16	15.3	14	100	--	--

Since the decline appears to have happened between 2013 and 2014, let's examine the 24 months from January 2013 to December 2014:

Month	Views of page Black	Views of page Blue	Views of page Brown	Views of page Green	Views of page Orange	Views of page Purple	Views of page Red	Views of page Violet	Views of page White	Views of page Yellow	Total	Percentage
201412	30K	41K	14K	27K	9.6K	28K	67K	3.1K	21K	19K	260K	2.4
201411	36K	46K	15K	31K	10K	35K	50K	3.7K	23K	22K	273K	2.5
201410	37K	52K	16K	34K	10K	34K	51K	4.5K	25K	26K	289K	2.7
201409	37K	57K	16K	35K	9.9K	37K	45K	4.8K	27K	29K	298K	2.8
201408	33K	47K	14K	34K	8.5K	31K	38K	3.9K	21K	22K	253K	2.4
201407	33K	47K	14K	30K	9.3K	31K	37K	4.2K	22K	22K	250K	2.3
201406	32K	49K	14K	31K	10K	34K	39K	4.9K	23K	22K	259K	2.4
201405	44K	55K	17K	37K	10K	51K	42K	5.2K	26K	26K	314K	2.9
201404	34K	60K	17K	36K	14K	38K	47K	5.8K	27K	28K	306K	2.8
201403	37K	136K	19K	51K	14K	123K	52K	5.5K	30K	31K	497K	4.6
201402	38K	58K	19K	39K	13K	41K	49K	5.6K	29K	29K	321K	3
201401	40K	60K	19K	36K	14K	40K	50K	4.4K	27K	28K	319K	3
201312	62K	67K	17K	44K	12K	48K	48K	4.4K	42K	26K	372K	3.5
201311	141K	96K	20K	65K	11K	68K	55K	5.3K	71K	34K	566K	5.3
201310	145K	102K	21K	69K	11K	77K	59K	5.7K	71K	36K	598K	5.6
201309	98K	80K	17K	60K	11K	53K	51K	4.9K	45K	30K	450K	4.2
201308	109K	87K	20K	57K	20K	57K	60K	4.6K	53K	28K	497K	4.6
201307	107K	92K	21K	61K	11K	66K	65K	4.6K	61K	30K	520K	4.8
201306	115K	106K	22K	69K	13K	73K	64K	5.5K	70K	33K	571K	5.3
201305	158K	122K	24K	79K	14K	83K	69K	11K	77K	39K	677K	6.3
201304	151K	127K	28K	83K	14K	86K	74K	12K	78K	40K	694K	6.4
201303	155K	135K	31K	92K	15K	99K	84K	12K	80K	43K	746K	6.9
201302	152K	131K	31K	84K	28K	95K	84K	17K	77K	41K	740K	6.9
201301	129K	126K	32K	81K	19K	99K	84K	9.6K	70K	42K	691K	6.4
Total	2M	2M	476K	1.3M	314K	1.4M	1.4M	152K	1.1M	728K	11M	100
Percentage	18.1	18.4	4.4	11.8	2.9	13.3	12.7	1.4	10.2	6.8	100	--
Tags	Colors	Colors	Colors	Colors	Colors	Colors	Colors	Colors	Colors	Colors	--	--

As we can see, the decline appears to have begun around March 2013 and then continued steadily till about June 2014, at which numbers stabilized to their lower levels.

A few sanity checks on these numbers:

The trends appear to be similar for different colors, with the notable difference that the proportional drop was higher for the more viewed color pages. Thus, for instance, black and blue saw declines from 129K and 126K to 30K and 41K respectively (factors of four and three respectively) from January 2013 to December 2014. Orange and yellow, on the other hand, dropped by factors of close to two. The only color that didn't drop significantly was red (it dropped from 84K to 67K, as opposed to factors of two or more for other colors), but this seems to have been partly due to an unusually large amount of traffic in the end of 2014. The trend even for red seems to suggest a drop similar to that for orange.
The overall proportion of views for different colors comports with our overall knowledge of people's color preferences: blue is overall a favorite color, and this is reflected in its getting the top spot with respect to pageviews.
The pageview decline followed a relatively steady trend, with the exception of some unusual seasonal fluctuation (including an increase in October and November 2013).

One might imagine that this is due to people shifting attention from the English-language Wikipedia to other language Wikipedias, but most of the other major language Wikipedias saw a similar decline at a similar time. More details are in my longer version of this post on my personal site.

Geography: continents and subcontinents, countries, and cities

Here are the views of some of the world's most populated countries between 2008 and 2014, showing that the peak happened as far back as 2010:

Page name	Pageviews in year 2014	Pageviews in year 2013	Pageviews in year 2012	Pageviews in year 2011	Pageviews in year 2010	Pageviews in year 2009	Pageviews in year 2008	Total	Percentage	Tags
China	5.7M	6.8M	7.8M	6.1M	6.9M	5.7M	6.1M	45M	9	Countries
India	8.8M	12M	12M	11M	14M	8.8M	7.6M	73M	14.5	Countries
United States	13M	15M	18M	18M	34M	16M	15M	129M	25.7	Countries
Indonesia	5.3M	5.2M	3.7M	3.6M	4.2M	3.1M	2.5M	28M	5.5	Countries
Brazil	4.8M	4.9M	5.3M	5.5M	7.5M	4.9M	4.3M	37M	7.4	Countries
Pakistan	2.9M	4.5M	4.4M	4.3M	5.2M	4M	3.2M	28M	5.7	Countries
Bangladesh	2.2M	2.9M	3M	2.8M	2.9M	2.2M	1.7M	18M	3.5	Countries
Russia	5.6M	5.6M	6.5M	6.8M	8.6M	5.4M	5.8M	44M	8.8	Countries
Nigeria	2.6M	2.6M	2.9M	3M	3.5M	2.6M	2M	19M	3.8	Countries
Japan	4.8M	6.4M	6.5M	8.3M	10M	7.3M	6.6M	50M	10	Countries
Mexico	3.1M	3.9M	4.3M	4.3M	5.9M	4.7M	4.5M	31M	6.1	Countries
Total	59M	69M	74M	74M	103M	65M	59M	502M	100	--
Percentage	11.7	13.8	14.7	14.7	20.4	12.9	11.8	100	--	--

Of these countries, China, India and the United States are the most notable. China is the world's most populous. India has the largest population with some minimal English knowledge and legally (largely) unfettered Internet access to Wikipedia, while the United States has the largest population with quality Internet connectivity and good English knowledge. Moreover, in China and India, Internet use and access have been growing considerably in the last few years, whereas it has been relatively stable in the United States.

It is interesting that the year with the maximum total pageview count was as far back as 2010. In fact, 2010 was so significantly better than the other years that the numbers beg for an explanation. I don't have one, but even excluding 2010, we see a declining trend: gradual growth from 2008 to 2011, and then a symmetrically gradual decline. Both the growth trend and the decline trend are quite similar across countries.

We see a similar trend for continents and subcontinents, with the peak occurring in 2010. In contrast, the smaller counterparts, such as cities, peaked in 2013, similarly to colors, and the drop, though somewhat less steep than with colors, has been quite significant. For instance, a list for Indian cities shows that the total pageviews for these Indian cities declined from about 20 million in 2013 (after steady growth in the preceding years) to about 13 million in 2014.

Some niche topics where pageviews haven't declined

So far, we've looked at topics where pageviews have been declining since at least 2013, and some that peaked as far back as 2010. There are, however, many relatively niche topics where the number of pageviews has stayed roughly constant. But this stability itself is a sign of decay, because other metrics suggest that the topics have experienced tremendous growth in interest. In fact, the stability is even less impressive when we notice that it's a result of a cancellation between slight declines in views of established pages in the genre, and traffic going to new pages.

For instance, consider some charity-related pages:

Page name	Pageviews in year 2014	Pageviews in year 2013	Pageviews in year 2012	Pageviews in year 2011	Pageviews in year 2010	Pageviews in year 2009	Pageviews in year 2008	Total	Percentage	Tags
Against Malaria Foundation	5.9K	6.3K	4.3K	1.4K	2	0	0	18K	15.6	Charities
Development Media International	757	0	0	0	0	0	0	757	0.7	Pages created by Vipul Naik Charities
Deworm the World Initiative	2.3K	277	0	0	0	0	0	2.6K	2.3	Charities Pages created by Vipul Naik
GiveDirectly	11K	8.3K	2.6K	442	0	0	0	22K	19.2	Charities Pages created by Vipul Naik
International Council for the Control of Iodine Deficiency Disorders	1.2K	1	2	2	0	1	2	1.2K	1.1	Charities Pages created by Vipul Naik
Nothing But Nets	5.9K	6.6K	6.6K	5.1K	4.4K	4.7K	6.1K	39K	34.2	Charities
Nurse-Family Partnership	2.9K	2.8K	909	30	8	72	63	6.8K	5.9	Pages created by Vipul Naik Charities
Root Capital	3K	2.5K	414	155	51	1.2K	21	7.3K	6.3	Charities Pages created by Vipul Naik
Schistosomiasis Control Initiative	4K	2.7K	1.6K	191	0	0	0	8.5K	7.4	Charities Pages created by Vipul Naik
VillageReach	1.7K	1.9K	2.2K	2.6K	97	3	15	8.4K	7.3	Charities Pages created by Vipul Naik
Total	38K	31K	19K	9.9K	4.6K	5.9K	6.2K	115K	100	--
Percentage	33.4	27.3	16.3	8.6	4	5.1	5.4	100	--	--

For this particular cluster of pages, we see the totals growing robustly year-on-year. But a closer look shows that the growth isn't that impressive. Whereas earlier, views were doubling every year from 2010 to 2013 (this was the take-off period for GiveWell and effective altruism), the growth from 2013 to 2014 was relatively small. And about half the growth from 2013 to 2014 was powered by the creation of new pages (including some pages created after the beginning of 2013, so they had more months in a mature state in 2014 than in 2013), while the other half was powered by growth in traffic to existing pages.

The data for philanthropic foundations demonstrates a fairly slow and steady growth (about 5% a year), partly due to the creation of new pages. This 5% hides a lot of variation between individual pages:

Page name	Pageviews in year 2014	Pageviews in year 2013	Pageviews in year 2012	Pageviews in year 2011	Pageviews in year 2010	Pageviews in year 2009	Pageviews in year 2008	Total	Percentage	Tags
Atlantic Philanthropies	11K	11K	12K	10K	9.8K	8K	5.8K	67K	2.1	Philanthropic foundations
Bill & Melinda Gates Foundation	336K	353K	335K	315K	266K	240K	237K	2.1M	64.9	Philanthropic foundations
Draper Richards Kaplan Foundation	1.2K	25	9	0	0	0	0	1.2K	0	Philanthropic foundations Pages created by Vipul Naik
Ford Foundation	110K	91K	100K	90K	100K	73K	61K	625K	19.5	Philanthropic foundations
Good Ventures	9.9K	8.6K	3K	0	0	0	0	21K	0.7	Philanthropic foundations Pages created by Vipul Naik
Jasmine Social Investments	2.3K	1.8K	846	0	0	0	0	5K	0.2	Philanthropic foundations Pages created by Vipul Naik
Laura and John Arnold Foundation	3.7K	13	0	1	0	0	0	3.7K	0.1	Philanthropic foundations Pages created by Vipul Naik
Mulago Foundation	2.4K	2.3K	921	0	1	1	10	5.6K	0.2	Philanthropic foundations Pages created by Vipul Naik
Omidyar Network	26K	23K	19K	17K	19K	13K	11K	129K	4	Philanthropic foundations
Peery Foundation	1.8K	1.6K	436	0	0	0	0	3.9K	0.1	Philanthropic foundations Pages created by Vipul Naik
Robert Wood Johnson Foundation	26K	26K	26K	22K	27K	22K	17K	167K	5.2	Philanthropic foundations
Skoll Foundation	13K	11K	9.2K	7.8K	9.6K	5.8K	4.3K	60K	1.9	Philanthropic foundations
Smith Richardson Foundation	8.7K	3.5K	3.8K	3.6K	3.7K	3.5K	2.9K	30K	0.9	Philanthropic foundations
Thiel Foundation	3.6K	1.5K	1.1K	47	26	1	0	6.3K	0.2	Philanthropic foundations Pages created by Vipul Naik
Total	556K	533K	511K	466K	435K	365K	340K	3.2M	100	--
Percentage	17.3	16.6	15.9	14.5	13.6	11.4	10.6	100	--	--

The dominant hypothesis: shift from non-mobile to mobile Wikipedia use

The dominant hypothesis is that pageviews have simply migrated from non-mobile to mobile. This is most closely borne by the overall data: total pageviews have remained roughly constant, and the decline in total non-mobile pageviews has been roughly canceled by growth in mobile pageviews. However, the evidence for this substitution doesn't exist at the level of individual pages because we don't have pageview data for the mobile domain before September 2014, and much of the decline occurred between March 2013 and June 2014.

What would it mean if there were an approximate one-on-one substitution from non-mobile to mobile for the page types discussed above? For instance, non-mobile traffic to colors dropped to somewhere between 1/3 and 1/2 of their original traffic level between January 2013 and December 2014. This would mean that somewhere between 1/2 and 2/3 of the original non-mobile traffic to colors has shifted to mobile devices. This theory should be at least partly falsifiable: if the sum of traffic to non-mobile and mobile platforms today for colors is less than non-mobile-only traffic in January 2013, then clearly substitution is only part of the story.

Although the data is available, it's not currently in an easily computable form, and I don't currently have the time and energy to extract it. I'll update this once the data on all pageviews since September 2014 is available on stats.grok.se or a similar platform.

Other hypotheses

The following are some other hypotheses for the pageview decline:

Google's Knowledge Graph: This is the hypothesis raised in Wikipediocracy, the Daily Dot, and the Register. The Knowledge Graph was introduced in 2012. Through 2013, Google rolled out snippets (called Knowledge Cards and Knowledge Panels) based on the Knowledge Graph in its search results. So if, for instance, you only wanted the birth date and nationality of a musician, Googling would show you that information right in the search results and you wouldn't need to click through to the Wikipedia page. I suspect that the Knowledge Graph played some role in the decline for colors seen between March 2013 and June 2014. On the other hand, many of the pages that saw a decline don't have any search snippets based on the Knowledge Graph, and therefore the decline for those pages cannot be explained this way.
Other means of accessing Wikipedia's knowledge that don't involve viewing it directly: For instance, Apple's Siri tool uses data from Wikipedia, and people making queries to this tool may get information from Wikipedia without hitting the encyclopedia. The usage of such tools has increased greatly starting in late 2012. Siri itself was released with the third generation iPad in September 2012 and became part of the iPhone released the next month. Since then, it has shipped with all of Apple's mobile devices and tablets.
Substitution away from Wikipedia to other pages that are becoming more search-optimized and growing in number: For many topics, Wikipedia may have been clearly the best information source a few years back (as judged by Google), but the growth of niche information sources, as well as better search methods, have displaced it from its undisputed leadership position. I think there's a lot of truth to this, but it's hard to quantify.
Substitution away from coarser, broader pages to finer, narrower pages within Wikipedia: While this cannot directly explain an overall decline in pageviews, it can explain a decline in pageviews for particular kinds of pages. Indeed, I suspect that this is partly what's going on with the early decline of pageviews (e.g., the decline in pageviews of countries and continents starting around 2010, as people go directly to specialized articles related to the particular aspects of those countries or continents they are interested in).
Substitution to Internet use in other languages: This hypothesis doesn't seem borne out by the simultaneous decline in pageviews for the English, French, and Spanish Wikipedia, as documented for the color pages.

It's still a mystery

I'd like to close by noting that the pageview decline is still very much a mystery as far as I am concerned. I hope I've convinced you that (a) the mystery is genuine, (b) it's important, and (c) although the shift to mobile is probably the most likely explanation, we don't yet have clear evidence. I'm interested in hearing whether people have alternative explanations, and/or whether they have more compelling arguments for some of the explanations proffered here.