As a result, when sound was added to the technology in the late 1920s, it was the English language which suddenly came to dominate the movie world. It is difficult to find accurate data, but several publications of the period provide clues. For example, in 1933 appeared the first edition of The Picturegoer's Who's Who and Encyclopaedia of the Screen Today. Of the 44 studios listed, 32 were American or British (the others were German and French). of the 2,466 artistes listed, only 85 (3 per cent) were making movies in languages other than English. Of the 340 directors, 318 (94 per cent) were involved only in English-language works. As an English-language reference book, there is bound to be some bias in the coverage – few movie stars are listed from non-European countries, for example – but the overall impression is probably not far from the truth.