 In 1985, the "Britannica" responded to reader requests by restoring the index as a two-volume set.The number of topics indexed by the "Britannica" has fluctuated from 500,000 (1985, the same as in 1954) to 400,000 (1989,1991) to 700,000 in the current 2007 print version.Presumably, this recent increase reflects the introduction of efficient electronic indexing, since the size of the encyclopedia has remained nearly constant at approximately 40 million words from 1954 to the present and far less than 40% of the encyclopedia has changed from 1985 to 2007.