Based in two sub-samples of Portuguese SMEs: 1) 495 young SMEs; and 2) 1350 old
SMEs, we conclude that age is a determinant factor in the relationships formed between
determinants and profitability. Age, size, liquidity and long-term debt are of greater
relative importance for the increased profitability of young SMEs, while risk is of
greater relative importance for the diminished profitability of this type of SME,
compared to the case of old SMEs. R&D expenditure is of greater relative importance
for increased profitability in old SMEs, this type of SME having more persistent
profitability, compared to the case of young SMEs
