The 55th anniversary edition of the Hot 100 All-Time Top Songs and Artists charts are based on actual performance on the weekly Billboard Hot 100, since the chart’s inception in August 1958 through the July 27, 2013 rankings. Songs are ranked based on an inverse point system, with weeks at No. 1 earning the greatest value and weeks at No. 100 earning the least. Due to changes in chart methodology over the Hot 100's 55 years (i.e., the inclusion of Nielsen Entertainment airplay monitoring and point-of-sales tracking and the recent inclusion of streaming data, among earlier modifications), certain eras are weighted differently to account for chart turnover rates over various periods. The Artist chart utilizes the same point system and adjusted weighting as the Songs list, but aggregates all titles for each act that charted over the course of its career.