This may be a very stupid question, and I've searched for an answer, which if there is way over my head. I seem to get a 100% discrepancy leaving all other inputs unchanged, if I use CPI (give twice as high a success rate) as a 3% inflation rate. I do understand that CPI does not include food and energy, but what I am trying to figure out is which (CPI or 3%) gives the most valid result. Thank you for your insight.