The year end charts as published by Billboard each year were necessarily limited.  In order to publish the chart the last week of December, the magazine stopped including rankings effectively the final week of November.  In some cases, this caused records whose popularity crossed over from one year to another to be underrated.  In some cases, these records ended up on the year end chart for two different years.  In some cases, the records were not included in either chart in spite of significant popularity.  The “Elvis Era Power Ranking” is an effort to correct this oversight by including all the weeks a record was on the charts, not just the weeks of a particular year.  The rating is based on the record's performance in the top twenty: 20 points for being #1, 19 for #2, etc. The record gets 5 additional points for each week it is in the top ten, 5 additional pointsfor each week it is #1, and one additional point for each week it was in the top forty.  In the case of the “cross-over” records, whether a record is included in the chart for the year it first entered or the year it last charted, the record was assigned the year in which it enjoyed its highest popularity.  In some cases, there were records that were so closely split that they were included on two year end charts.