# Saving Recall the income-expenditure identity `Y = C + I + G + NX` from [[national-accounting]], this doesn't mean that every group eats exactly the same piece of the pie that they got as an income stream. Notion of saving: the difference between a group's income and its expenditures. [[gdp|GDP]], [[gnp|GNP]], and [[nfp|NFP]]: GNP = GDP + NFP Definition: `S = Y + NFP - C - G`. Can derive: `S = I + NX + NFP = I + CA` (`CA = NX + NFP` = Current Account surplus) Saving is a flow variable! Two ways to accumulate wealth: - **`I`**: Investment into building up the capital stock of an economy (Gross Capital Formation) - **`CA`**: Acquiring claims against foreigners, against their GDP in the future.