Dear I have time series for Two variables some transformations are did for this variables I need clarification on it 1- percentage of global crude oil Transformation: raw data-- take ln for this series(why?!!)- take differences then multiply it by 1200( why they use this number (1200)!!! 2-real oil price Transformation: nominal real price/(CPI/100) why he divided the CPI by 100?? Thentake ln ( why)??? Then subtract the mean from series ( why) Then multiply again by 100(why) I hope my questions are clear