I'm trying not to have yearly data, to reduce the amount of
data I have to input into the model. So I have included datayears, in 5 years
periods. I know that if I include yearly data, then Times
interpolates/extrapolates the data to the milestone years. So, if I decide to
have datayears=milestone years every five years, for example, then I should be
doing the interpolation between the yearly data and the datayears included in
my model, am I right? In this case, what fomula should I use?

Up to now, my data is discounted and yearly, in constant dollars,
and I'm wondering if a simple average of the 5 year period is correct or If I
should use a different formula.

thanks

Sara

If you include yearly data, there is nothing left for TIMES to do by interpolation/extrapolation, because your data is already specified for the Milestone years.

Typically, the time series data used as input for TIMES represent future projections, which usually don't have any abrupt jumps, but are locally close to linear. In these cases you don't need to do any interpolation by yourself. However, if your input data includes time series that would be far from linear within some periods, you could use e.g. 5-year centered averages for converting the yearly data into a time series with data points having 5-year intervals. Optionally, you could use discount factors as weights in the calculation to get weighted 5-year centered averages.

Thank you very much, Antti