Joe Carter points to a Lifehacker article that sums up two basic equations that lead to the creation of wealth (with what I consider to be a clarifying correction applied in the first formula):
Income > spending = surplus
Surplus x time = wealth
Likewise, Wilhelm Röpke, in his A Humane Economy, points to two equations arising from classical literature that connect surplus with happiness and deficit to misery (the Micawber Principle).
According to Mr. Micawber from Dickens’ David Copperfield:
Annual income £20, annual expenditure £19.975 = happiness
Annual income £20, annual expenditure £20.025 = misery
Now it is true, of course, that material excess does not guarantee happiness any more than material want guarantees misery. This is particularly true of happiness and misery in the most important sense, that of eternal, spiritual felicity or calamity.
But as human beings, with both material as well as spiritual concerns, the state of our body and bodily does have implications for our happiness here below. This is in part why the Bible describes the relationship between the borrower and the lender in such stark terms. And as Röpke argues, this holds true for at both the level of individuals as well as institutions.