The recurrent rule on the Hot 100 indicates that descending songs are removed once they fall below number 25 after 52 weeks, or once below number 50 after 20 weeks.[8] The chart does not factor in any form of radio airplay, as, according to MRC Data, "The focus was on metrics that could be systematically measured in each country", considering how "unlike streaming and download sales, radio is not reliably measured at this time [2020] in many territories and, even if tracked, is not done consistently from country to country".[7] As such, the chart has been noted for being similar to the Rolling Stone Top 100, which, although it is a US song chart, also only incorporates sales and streams in their chart formula.[7][dubious ]