Rankings do decay. Top Grossing rankings are consistent because the top apps have a large user base, from which a small fraction will purchase the iAPs. Those a

Rankings do decay. Top Grossing rankings are consistent because the top apps have a large user base, from which a small fraction will purchase the iAPs. Those apps do make the most amount of money in the days before. Free/Paid charts change all the time -- the apps that show up there get the most amount of downloads.