The power of big data and psychological profiling may be transforming the face of politics and the mainstream media, but it’s very difficult to say so with much certainty.

Earlier this year, Motherboard republished a long piece, originally written in German for a Swiss publication called Das Magazin. It described in some detail how the big data company Cambridge Analytica had helped Donald Trump to victory during his election campaign. On its website, Cambridge Analytica claims to have gathered psychological profiles, based on 5,000 separate pieces of data, about 220 million American citizens. The theory: if you understand how a person thinks, you can send them a targeted ad that truly sways their opinion.

Now, the Guardian has written a long report that details that the company’s psychological tentacles reach out much further. It claims that Robert Mercer, the computer scientist turned hedge fund manager, is “at the heart of a multi-million-dollar propaganda network” that is shaping the political and media landscape—of which Cambridge Analytica is just a single component.

Mercer has invested in Cambridge Analytica. And he also kick-started Steve Bannon’s Breitbart news organization. In theory, a site creating right-wing news combined with a finely tuned system for delivering it with laser-guided precision could create a potent propaganda machine. But it’s not clear that Cambridge Analytica’s psychological profiling actually adds much value to the process.

Last year, we argued that there wasn’t any published data to prove that what Cambridge Analytica is doing would add much weight to Trump’s ability to score votes. At the time, Daniel Kreiss, a professor of political communication at the University of North Carolina, Chapel Hill, argued that “basic categories of data tend to be very predictive,” while “everything else gives you only marginal potential advantages." More recently, Buzzfeed interviewed a number of ex-Cambridge Analytica employees, as well as other consultants who had seen its work, and found that “the company has never provided evidence that [its psychological approach] even works.” In other words, Cambridge Analytica's targeting may not be doing a great deal more than other approaches that are widely used around the Internet.

It is certainly an attractive proposition to blame big data and psychological profiling for shifts in the political and media landscapes that one finds troubling, rather than believe that there is a large and worrying socio-economic divide in the West. But it’s also unwise to do so without data to support the case.

(Read more: Guardian, Buzzfeed, Motherboard, “How Political Candidates Know If You’re Neurotic,” “Is 2016 the Year of Psychological Profiling?”)