This one is harder, how can you measure earning media and its impact? There are a suite of tools available for measuring press mentions. Because of the separation of church and state, that is the division between commercial arms and journalist arms in publishers. The data has to be from third parties or inferred using other signals.
Often the number of social shares is a signal, to go if this media coverage was effective it should have generated some shares.
Some platforms like Nudge, have built predictive measures, where they can analyze the content and predict based on similar types of content how well each piece did.
This is the two-pronged approach to understanding the impact of earned media.
The other downstream metric, is looking at search traffic, during a press mention did my search traffic change significantly? This isn’t helpful for lots of press mentions but for notable ones if it can provide some context.