  In this document we propose a new improvement for boosting techniques as
proposed in Friedman '99 by the use of non-convex cost functional. The idea is
to introduce a correlation term to better deal with forecasting of additive
time series. The problem is discussed in a theoretical way to prove the
existence of minimizing sequence, and in a numerical way to propose a new
"ArgMin" algorithm. The model has been used to perform the touristic presence
forecast for the winter season 1999/2000 in Trentino (italian Alps).
