A common approach is to forecast  by analogy, using data for similar products that have been on the market previously.
( ( A ( common approach ) ) ( ( is ( to ( ( ( forecast ( by analogy ) ) , ) ( using ( ( data ( for ( similar products ) ) ) ( that ( have ( ( been ( on ( the market ) ) ) previously ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (JJ common) (NN approach)) (VP (VBZ is) (S (VP (TO to) (VP (VB forecast) (PP (IN by) (NP (NN analogy))) (, ,) (S (VP (VBG using) (NP (NP (NNS data)) (PP (IN for) (NP (JJ similar) (NNS products))) (SBAR (WHNP (WDT that)) (S (VP (VBP have) (VP (VBN been) (PP (IN on) (NP (DT the) (NN market))) (ADVP (RB previously))))))))))))) (. .)))
Similar products usually have the same type of demand.
( ( Similar products ) ( usually ( ( have ( ( the ( same type ) ) ( of demand ) ) ) . ) ) )
(ROOT (S (NP (JJ Similar) (NNS products)) (ADVP (RB usually)) (VP (VBP have) (NP (NP (DT the) (JJ same) (NN type)) (PP (IN of) (NP (NN demand))))) (. .)))