One of the reasons why I wrote the Inbound PR book was to help PR professionals open their eyes to the need for modern measurement and tangible proof of PR results. Inbound Marketing is terrific at showing the monetary value of marketing efforts so there's a lot that PR could learn.
Measurement has always been a problem in PR. For years, PR pros have used fluffy metrics (and some continue doing so). Those metrics are not what C-level people care about, they're not what will get you budget.
There's also been a lot of effort put in from the PR industry itself to solve this problem.
One such example are the Barcelona Principles. They were first introduced by AMEC in 2010 and recently got their third refresh.
Let's take a look at them: