Martin Sandbu at the FT says “It is now fair to say that the debate on the economics has been won by the Remain side.” He was of course talking about what the Bank of England said yesterday, rather than the 196 economists who signed our letter, but together they present an important test for the non-partisan media. The extreme difference between the amount of coverage the Bank got (blanket) and our letter got (practically zero) tells us something important about how media coverage works: the Bank is after all just a collection of economists.  (The list of those who signed our letter can be obtained from here.)
The media will not, of course, go as far as Martin and say the economic argument has been won. But what they can say is that all the leading economic institutions and the overwhelming majority of academic economists think that Brexit will involve significant short term and long term costs. That is now a statement of fact, which readers of some very non-partisan tabloids may not be aware of. My guess would be that there are at least 25 academic economists who think Brexit will involve significant costs compared to each one who thinks it will bring benefits. As I said here, that is as close to unanimity among economists as you will ever get. As it is a fact, saying that it appears to be so in no way breaches impartiality.
They could go further. The main response of the Leave campaign has been to say all economic forecasts are hopeless. They are no doubt referring to unconditional macro forecasts of the ‘what will growth be next year’ type. However the assessments made by all these economists and economic institutions are not unconditional forecasts, but conditional forecasts: what difference will Brexit make. They are much more reliable than unconditional forecasts. (This point can be got across with simple analogies: a doctor will tell you that being overweight increases the chance of a heart attack, but not when you will have one.)
So trying to discount the near universal assessment of economists by referring to macro forecasts either represents dangerous ignorance or deliberate obfuscation. But for those with little knowledge of these things, it is a deception that could work. Pointing out the difference does not breach impartiality, but informs the debate.
Brexit in the UK, and Trump in the US, represents a critical challenge to the ‘shape of the earth: views differ’ style of reporting. ‘Balance’ should never involve ignoring facts that are awkward for one side, or not challenging statements that are false. How many journalists (particularly political journalists) recognise this may determine two critical elections for both the UK and the whole world.
 Of course letters are not random samples, but it is not often you get letters from 170+ academic economists. The letter is important because academic economists are hardly part of the establishment, and indeed academics are usually able to say what they think without fear of any consequences.