It is what consumers are prepared to pay for consumer goods that determines how much factors will be paid. And how much each factor is paid out of consumer spending is determined by the value of its marginal product, i.e., its contribution to the final product. The market process works to bring factor prices in to line with the value of factor output. It follows that only by raising the value of labor's marginal product can we raise real wages. And this brings us right back to investment.
Investment is the process by which present goods are transformed into future goods, capital goods.
It is this spending that raises the value of labor's marginal product. Hence, by increasing individual output, purchasing power is increased which raises the demand for other products. This demolishes the idea that increased investment lowers real wages and raises unemployment. It follows from this that any resistance by unions to falling real incomes will only succeed in raising unemployment. This is something that many socialists welcome because it allows them to lay the blame on the on free market.