If, as Marx advocated, “surplus value” were returned to workers, how might this slow the economic growth and development? Or would it?

In Marxian economics, surplus value is the difference between the amount raised through a sale of a product and the amount it cost to the owner of that product to manufacture it: i.e. the amount raised through sale of the product minus the cost of the materials, plant and labour power. The concept originated in Ricardian socialism, with the term "surplus value" itself being coined by William Thompson in 1824; however, it was not consistently distinguished from the related concepts of surplus labor and surplus product. The concept was subsequently developed and popularized by Karl Marx. Marx's formulation is the standard sense and the primary basis for further developments, though how much of Marx's concept is original and distinct from the Ricardian concept is disputed (see § Origin). Marx's term is the German word "Mehrwert", which simply means value added (sales revenue less the cost of materials used up), and is cognate to English "more worth".