10.4 The national saving and investment identity  (Page 4/16)

Short-term movements in the business cycle and the trade balance

In the short run, trade imbalances can be affected by whether an economy is in a recession or on the upswing. A recession tends to make a trade deficit smaller, or a trade surplus larger, while a period of strong economic growth tends to make a trade deficit larger, or a trade surplus smaller.

As an example, note in [link] that the U.S. trade deficit declined by almost half from 2006 to 2009. One primary reason for this change is that during the recession, as the U.S. economy slowed down, it purchased fewer of all goods, including fewer imports from abroad. However, buying power abroad fell less, and so U.S. exports did not fall by as much.

Conversely, in the mid-2000s, when the U.S. trade deficit became very large, a contributing short-term reason is that the U.S. economy was growing. As a result, there was lots of aggressive buying in the U.S. economy, including the buying of imports. Thus, a rapidly growing domestic economy is often accompanied by a trade deficit (or a much lower trade surplus), while a slowing or recessionary domestic economy is accompanied by a trade surplus (or a much lower trade deficit).

When the trade deficit rises, it necessarily means a greater net inflow of foreign financial capital . The national saving and investment identity teaches that the rest of the economy can absorb this inflow of foreign financial capital in several different ways. For example, the additional inflow of financial capital from abroad could be offset by reduced private savings, leaving domestic investment and public saving unchanged. Alternatively, the inflow of foreign financial capital could result in higher domestic investment, leaving private and public saving unchanged. Yet another possibility is that the inflow of foreign financial capital could be absorbed by greater government borrowing, leaving domestic saving and investment unchanged. The national saving and investment identity does not specify which of these scenarios, alone or in combination, will occur—only that one of them must occur.

Key concepts and summary

The national saving and investment identity is based on the relationship that the total quantity of financial capital supplied from all sources must equal the total quantity of financial capital demanded from all sources. If S is private saving, T is taxes, G is government spending, M is imports, X is exports, and I is investment, then for an economy with a current account deficit and a budget deficit:

Problems