Actually there is I would suggest a better number than 2% to use as a historical demand predictor....

If you look at global per capita oil consumption since about 1971 to current vs global population you will see it is as close as you get in the real world to a perfect fit:

4.1 bbls /person/ year +/- 0.25 bbls/year with R^2 > 0.91
(consumption from BP review, world population from US Census dept.)

BUT world population is growing at about 1.275% per year exponential, not 2%, so I'd suggest that as a benchmark, unless there is a better explanation for where 2% is being drawn from....

P.S. I can't find an equation that describes the price-production relationship at the level of yearly summary figures in this time period that is anything like a good fit, if someone knows of such a thing do tell...