Fertility projections often involve the forecasting of age-specific fertility rates. This may be done to take advantage of the known age structure of the existing female population in using the cohort-component approach to fertility projection, or because age-specific fertility is itself of interest. If rates for single years of age are used, this creates a forecasting problem of large dimension, with fertility rates for 30 or more ages to forecast. If long-term projections are being made, care must also be taken to insure that projections for different ages are consistent in the sense of the long-term shape of fertility across age looking reasonable in comparison to historical data.