Each January, Bachtrack publishes statistics for its listings for the year just ended. Alan Teder, who manages the Arvo Pärt Fan Page, reports on Facebook:

They don't say it explicitly in this Bachtrack article on 2014 performance statistics, but on Twitter Bachtrack confirmed that Estonian composer Arvo Pärt is No. 1 of the living composers with the most works performed for the 4th year running (i.e. 2011 to 2014).

Arvo Pärt is No. 37th in the list of all composers. John Williams and John Adams are No. 2 and No. 3 respectively in living composers.

Bachtrack.com calculates a series of statistics each year based exclusively on performances listed on Bachtrack.

http://bachtrack.com/classical-music-statistics-2014