Project or Extrapolate Into the Future

Can I use Joinpoint to project or extrapolate into the future?

Answer:

While the Joinpoint program itself does not do projections/extrapolations, it is not unreasonable to use Joinpoint to project a few years into the future. To do so, one would need to extrapolate the final segment, and compute the standard errors of the projection, using the betas displayed in the output. The Joinpoint Team has had some success using Joinpoint for projections (validated against actual values when the data is rolled back several years so the projected values can be validated against actual values). However, a projection using Joinpoint may or may not be more accurate than other methods (e.g. time series methods), depending on the situation. Long term projections using Joinpoint are not advised. Also, AAPCs, since they are summary measures over an interval, are not as appropriate to use for projections as is the APC of the final segment.

References which used Joinpoint for projections are:

Chen HS, Portier K, Ghosh K, Naishadham D, Kim HJ, Zhu L, Pickle LW, Krapcho M, Scoppa S, Jemal A, Feuer EJ. Predicting US- and state-level cancer counts for the current calendar year: Part I: evaluation of temporal projection methods for mortality. Cancer 2012 Feb 15;118(4):1091-9. [Full Text]

Zhu L, Pickle LW, Ghosh K, Naishadham D, Portier K, Chen HS, Kim HJ, Zou Z, Cucinelli J, Kohler B, Edwards BK, King J, Feuer EJ, Jemal A. Predicting US- and state-level cancer counts for the current calendar year: Part II: evaluation of spatiotemporal projection methods for incidence. Cancer 2012 Feb 15;118(4):1100-9. [Full Text]