Less a consultant firm, more an economic institute. This has nothing to do with consumerism, cars televisions, or what they want. If it was based on what people wanted then the living wage would probably be much higher. It's all about what people need to live a basic lifestyle. That is to say one in which they aren't threatened by poverty.
Your position could be defined as the general standard of living 𝑋₁ minus some constant 𝐶. In which case, 𝑋ₙ would equal 𝑋ₙ₋₁ − 𝑘𝐶―leaving the general standard of living to decline
ad infinitum.