This is just one opinion.(posted 8173 days ago)I don't use that phrase but silver content can be measured. Manufacturers also know it. AGFA for example publishes their technical data sheets containing silver content (don't remember about films; they give numbers at least for papers).
One of important characteristics of paper is maximum density. Some people believe more silver means richer black. It's not the case. If you coat your paper using the same emulsion but different thickness, they may be directly related. But manufacturers have so many other things to tweak besides silver content.
About films, many people don't take advantage of really dense area, and many prefer relatively thin negatives. So, it seems reasonable to think D-max is not the most important spec to be improved. (e.g. APX25 has low maximum density yet many people love it.)
If anyone has an argument why silver rich material is preferred (for general or specific situation) regardless of D-max, I am very interested to hear it.