Social Value & its Variability

I am one of those people, as the article identifies, that approaches social value as "subjective, malleable, and variable." Although I believe social value is all of these things, I think this is what makes it even more difficult to create better metrics to capture it. How do you measure something that is subjective, malleable, and variable. Will the metrics not continuously change due to the variability of the subject? Also, how do you measure such a thing that is variable but also has so many outside factors such as the environment affecting it? These are the many questions that are running through my mind when thinking of my venture. I know what I would like the social outcome to result from The People's Station, however I am not sure about the route to take in measuring it as well as how I would remove outside factors, such as other programs, that will also be effective in changing the social outcome of my target population.