Just measure and plot it out?

I don't think it's an accurate measurement for a flip however, which is short term.

Within the last year is not a good measuring stick. 

Further disadvantage is that you need approval for many measures, like changing windows, putting air con, etc.

@Drew SygitHi Drew,Regarding why we would still use a 'measuring stick' as to how much income our tenant makes is simply we want to make sure our tenant can afford the property.  

They come measure and give you a free sink, and the 4 inch backsplash really makes the entire room sparkle.

There is no universal standard of measurement for this, and most people using this type of system are going to mold it to fit their own criteria or agenda.

Refunds are utterly irrelevant in measuring your tax efficiency.

Commercial will be monetized based upon revenue potential's, and fact is affordability in most places is pressing the glass ceiling, or broken above, that affordability measure that will only go higher as median incomes go up. 

- Upgrade older appliances to more efficient models.Cost-Saving Measure: - Energy-efficient appliances consume less electricity, reducing utility bills