"Did more PS3 or Xbox 360 owners apparently purchase Portal 2 during its 11 days on the market in April? Let's take a look!" says CoffeeWithGames in the introduction section.
"The charts above show the sales ranks for Portal 2 on the PS3 and Xbox 360, with sales ranks recorded from April 19 through April 30, 2011. The sales ranks were recorded from Amazon.com's "Top 100" video game ranks each day(one day twice!), along with the dates and times, as well as sales prices for each game.", says CWG when talking about the chart(s) included.