Dear Statalist.
I have a panel data set containing artists, album releases by artists, and the year of each album release.
I need to calculate a variable "wanted" that shows the average time between the artists' album releases in the data set.
I am trying to get a sense of the average time an artist spends in between releases.
Some artists only release a single album.

The following toy data set shows the structure of the data:
artist_id album_id year
1 1 2000
1 2 2003
1 3 2007
2 4 1996
3 5 2005
3 6 2010
3 7 2011
Any and all suggestions on this problem would be greatly appreciated.
Thank you!

Kind regards,
Erik