1. "Users." Google replaced the term "unique visitors” with "users" on Apr. 16, 2014 and said the terms mean the same thing. "Unique visitors" (aka "users") are defined by Google Analytics as (as of June 27, 2013): "Unique Visitors represents the number of unduplicated (counted only once) visitors to your website over the course of a specified time period. A Unique Visitor is determined using cookies." ProCon.org determines unique visitors each month then adds all the monthly data together for the year's total.
2. "Pageviews" are defined by Google Analytics as (as of June 27, 2013): "Pageviews is the total number of pages viewed. Repeated views of a single page are counted."
3. "Hits" are defined by Google Analytics as (as of May 16, 2012): "A request to the web server for a file. This can be an HTML page, an image (jpeg, gif, png, etc.), a sound clip, a cgi script, and many other file types. An HTML page can account for several hits: the page itself, each image on the page, and any embedded sound or video clips. Therefore, the number of hits a website receives is not a valid popularity gauge, but rather is an indication of server use and loading."
4. Extrapolations. While ProCon.org traffic software has tracked sessions from July 2004 through May 2013, it has not always tracked unique visitors, pageviews, and hits. Some of the traffic data (unique visitors, 2004-2007; pageviews and hits, 2004-2005) were extrapolated based on their relation to sessions traffic.
5. Change in Recording Web Traffic at ProCon.org: On June 27, 2013, ProCon.org began using "unique visitors” and "pageviews” from Google Analytics instead of "sessions” and "pageviews” from Google’s Urchin program as our primary measure of web traffic.
Although Urchin still functions, it is no longer updated or supported by Google. Plus, their term "sessions” has fallen out of common use as a measurement and the terms "unique visitors” and "pageviews” have become the norm. We will continue to report "hits” from Urchin on a quarterly basis on this page; we will no longer track "sessions."
Urchin’s server-based method of recording traffic produced a significantly higher pageview counts than the browser-based recording used by Analytics. Given the popularity of Google Analytics, we have opted to use their pageview numbers, even though those numbers are lower, so that we can more accurately compare ourselves against the many other websites that use Google Analytics.
6. Totals from 2004 to 2013 included traffic from two websites that we no longer track as of Jan. 1, 2014. The Rose Bird website (www.rosebirdprocon.org), between 2004 and 2013, had (in order of year): 493; 1,862; 2,682; 4,371; 6,688; 8,026; 11,598; 11,609; 2,148; and 1,751 pageviews, respectively. The Nuclear Power website (www.nuclearpowerprocon.org), between 2004 and 2013, had (in order of year): 3,243; 15,220; 21,917; 35,725; 54,659; 65,591; 59,920; 85,246; 30,104; and 30,877 pageviews, respectively. Steve Markoff , who later would found and chair ProCon.org, created two pro-con style booklets about Rose Bird and Nuclear Power in the 1980s and converted them into websites in 2002. Although related and predecessors to ProCon.org, we decided to exclude traffic from those two websites for our totals (effective Jan. 1, 2014) because the research and the websites were not developed by ProCon.org which did not exist prior to July 12, 2004.