We are often asked where to get the data that describes the uncertainty of a particular variable used in a model. We don't know as much as we would like.
Some data are easy to get, some are hard.
It is now a task of the financial planning profession to develop the information and resources to provide this data. Below we tell you what the sponsors are doing. The current situation is not completely satisfactory. If you have a good source of data for a variable, please contact us. Ibbotson , or from your investment professional.