and I'm not talking about top tracks playlist for a certain country. Just curious in general. Is the selection criteria of songs based on:
1. how many times certain songs were played in a year on Spotify?
2. how many times people added these songs on their playlists or saved/ favorited them?
3. is there an external index involved as well (such as the billboard) that helps certain songs be included in these playlists around the end of year