ArtReview magazine has published its 15th annual Power 100 list, ranking the art world's most important players. Hans Ulrich Obrist, the artistic director of the Serpentine Galleries in London, takes the number-one spot this year, reclaiming his position from 2009. 

The magazine’s editors write: “The curator is famous for ignoring traditional constraints of both time (he works nearly constantly, and famously founded the Brutally Early Club, an open-to-all discussion group that meets at 6.30am) and geographic place (he is in perpetual motion, giving talks and doing interviews at nearly every significant art event around the globe), and a single institution could never hope to house the full breadth of his activities.” 

Three artists—Hito Steyerl (7), Wolfgang Tillmans (9) and Ai Weiwei (10)—are in the top ten this year, while new entrants include Ed Atkins (50), the Indian group Raqs Media Collective (number 86), the South African artist Zanele Muholi (95) and the Icelandic artist Ragnar Kjartansson (100).

On the institutional side, Frances Morris, the newly appointed director of Tate Modern, has landed in the number-five spot, which she shares with the outgoing director of Tate, Nicholas Serota. Writers making the list include the theorist Donna Haraway (43).