Hollywood's system of box office prediction, know as "tracking" is unfit for purpose in the digital age and needs radical overhaul, leading industry figures have said. According to a report in industry bible Variety, current practice "simply isn't capable of drilling down deeply enough to provide the kind of analytics that newer digitally driven data-collection can".

Complaints have surfaced during a summer of unexpected flops and surprise hits – for example, The Mortal Instruments: City of Bones was predicted to take $18m in its first five days at the US box office, but in the event took just $14m.

The estimates are important as they allow film distributors to plan their marketing and release strategies, but the polling-based system currently in use dates from the 1970s, and takes little account of the impact of social media.

Market research analysts suggest the real problem is that tracking was developed initially to gauge the effect of advertising on film-goers, and can only measure the vaguest kind of buzz – as well as being based only on cinema-released films. With the narrowing of the release window, the drop in DVD sales and the rise of VOD, accurate assessment of actual sales is not possible.

Variety quote Vincent Bruzzese, CEO of the Worldwide Motion Picture Group, as saying: "Simply knowing the awareness and interest of something only scratches the surface. It doesn't matter necessarily if you're going to definitely recommend a movie, so much as how you're going to recommend it." Recommendations via social media, he says, are more likely to result in purchases.

The report comes as part of a wider investigation of the ratings industry, spearheaded by major concern over TV audience data collectors Nielsen, whose apparent inability to record viewing figures for VOD and mobile have caused disquiet among TV executives. They depend on the information to calculate advertising rates and assess TV shows' success.