It's more difficult to quantify the human emotion created by brands than simpler metrics like revenue or page views, but it isn't impossible.There are a number of indirect proxy metrics you can use to reliably discover how your audience is relating to your brand. (entrepreneur.com)
Because oxygen is critical to many forms of life and geochemical processes, numerous models and indirect proxies for the oxygen content in the atmosphere have been developed over the years, but there was no consensus on whether oxygen concentrations were rising, falling or flat during the past million years (and before fossil fuel burning). (sciencedaily.com)