Excessive saving
To Keynes, excessive saving, i.e. saving beyond planned investment, was a serious problem, encouraging recession or even depression. Excessive saving results if investment falls, perhaps due to falling consumer demand, over-investment in earlier years, or pessimistic business expectations, and if saving does not immediately fall in step.
The classical economists argued that interest rates would fall due to the excess supply of "loanable funds." The first diagram, adapted from the only graph in The General Theory, shows this process. (For simplicity, other sources of the demand for or supply of funds are ignored here.) Assume that fixed investment in capital goods falls from "old I" to "new I" (step a). Second (step b), the resulting excess of saving causes interest-rate cuts, abolishing the excess supply: so again we have saving (S) equal to investment. The interest-rate fall prevents that of production and employment.
Keynes had a complex argument against this laissez-faire response. The graph below summarizes his argument, assuming again that fixed investment falls (step A). First, saving does not fall much as interest rates fall, since the income and substitution effects of falling rates go in conflicting directions. Second, since planned fixed investment in plant and equipment is mostly based on long-term expectations of future profitability, that spending does not rise much as interest rates fall. So S and I are drawn as steep (inelastic) in the graph. Given the inelasticity of both demand and supply, a large interest-rate fall is needed to close the saving/investment gap. As drawn, this requires a negative interest rate at equilibrium (where the new I line would intersect the old S line). However, this negative interest rate is not necessary to Keynes's argument.
Third, Keynes argued that saving and investment are not the main determinants of interest rates, especially in the short run. Instead, the supply of and the demand for the stock of money determine interest rates in the short run. (This is not drawn in the graph.) Neither change quickly in response to excessive saving to allow fast interest-rate adjustment.
Finally, because of fear of capital losses on assets besides money, Keynes suggested that there may be a "liquidity trap" setting a floor under which interest rates cannot fall. (In this trap, bond-holders, fearing rises in interest rates (because rates are so low), fear capital losses on their bonds and thus try to sell them to attain money (liquidity).) Even economists who reject this liquidity trap now realize that nominal interest rates cannot fall below zero (or slightly higher). In the diagram, the equilibrium suggested by the new I line and the old S line cannot be reached, so that excess saving persists. Some (such as Paul Krugman) see this latter kind of liquidity trap as prevailing in Japan in the 1990s.
Even if this "trap" does not exist, there is a fourth element to Keynes's critique (perhaps the most important part). Saving involves not spending all of one's income. It thus means insufficient demand for business output, unless it is balanced by other sources of demand, such as fixed investment. Thus, excessive saving corresponds to an unwanted accumulation of inventories, or what classical economists called a general glut. This pile-up of unsold goods and materials encourages businesses to decrease both production and employment. This in turn lowers people's incomes—and saving, causing a leftward shift in the S line in the diagram (step B). For Keynes, the fall in income did most of the job ending excessive saving and allowing the loanable funds market to attain equilibrium. Instead of interest-rate adjustment solving the problem, a recession does so. Thus in the diagram, the interest-rate change is small.
Whereas the classical economists assumed that the level of output and income was constant and given at any one time (except for short-lived deviations), Keynes saw this as the key variable that adjusted to equate saving and investment.
Finally, a recession undermines the business incentive to engage in fixed investment. With falling incomes and demand for products, the desired demand for factories and equipment (not to mention housing) will fall. This accelerator effect would shift the I line to the left again, a change not shown in the diagram above. This recreates the problem of excessive saving and encourages the recession to continue.
In sum, to Keynes there is interaction between excess supplies in different markets, as unemployment in labor markets encourages excessive saving—and vice-versa. Rather than prices adjusting to attain equilibrium, the main story is one of quantity adjustment allowing recessions and possible attainment of underemployment equilibrium.
The classical economists argued that interest rates would fall due to the excess supply of "loanable funds." The first diagram, adapted from the only graph in The General Theory, shows this process. (For simplicity, other sources of the demand for or supply of funds are ignored here.) Assume that fixed investment in capital goods falls from "old I" to "new I" (step a). Second (step b), the resulting excess of saving causes interest-rate cuts, abolishing the excess supply: so again we have saving (S) equal to investment. The interest-rate fall prevents that of production and employment.
Keynes had a complex argument against this laissez-faire response. The graph below summarizes his argument, assuming again that fixed investment falls (step A). First, saving does not fall much as interest rates fall, since the income and substitution effects of falling rates go in conflicting directions. Second, since planned fixed investment in plant and equipment is mostly based on long-term expectations of future profitability, that spending does not rise much as interest rates fall. So S and I are drawn as steep (inelastic) in the graph. Given the inelasticity of both demand and supply, a large interest-rate fall is needed to close the saving/investment gap. As drawn, this requires a negative interest rate at equilibrium (where the new I line would intersect the old S line). However, this negative interest rate is not necessary to Keynes's argument.
Third, Keynes argued that saving and investment are not the main determinants of interest rates, especially in the short run. Instead, the supply of and the demand for the stock of money determine interest rates in the short run. (This is not drawn in the graph.) Neither change quickly in response to excessive saving to allow fast interest-rate adjustment.
Finally, because of fear of capital losses on assets besides money, Keynes suggested that there may be a "liquidity trap" setting a floor under which interest rates cannot fall. (In this trap, bond-holders, fearing rises in interest rates (because rates are so low), fear capital losses on their bonds and thus try to sell them to attain money (liquidity).) Even economists who reject this liquidity trap now realize that nominal interest rates cannot fall below zero (or slightly higher). In the diagram, the equilibrium suggested by the new I line and the old S line cannot be reached, so that excess saving persists. Some (such as Paul Krugman) see this latter kind of liquidity trap as prevailing in Japan in the 1990s.
Even if this "trap" does not exist, there is a fourth element to Keynes's critique (perhaps the most important part). Saving involves not spending all of one's income. It thus means insufficient demand for business output, unless it is balanced by other sources of demand, such as fixed investment. Thus, excessive saving corresponds to an unwanted accumulation of inventories, or what classical economists called a general glut. This pile-up of unsold goods and materials encourages businesses to decrease both production and employment. This in turn lowers people's incomes—and saving, causing a leftward shift in the S line in the diagram (step B). For Keynes, the fall in income did most of the job ending excessive saving and allowing the loanable funds market to attain equilibrium. Instead of interest-rate adjustment solving the problem, a recession does so. Thus in the diagram, the interest-rate change is small.
Whereas the classical economists assumed that the level of output and income was constant and given at any one time (except for short-lived deviations), Keynes saw this as the key variable that adjusted to equate saving and investment.
Finally, a recession undermines the business incentive to engage in fixed investment. With falling incomes and demand for products, the desired demand for factories and equipment (not to mention housing) will fall. This accelerator effect would shift the I line to the left again, a change not shown in the diagram above. This recreates the problem of excessive saving and encourages the recession to continue.
In sum, to Keynes there is interaction between excess supplies in different markets, as unemployment in labor markets encourages excessive saving—and vice-versa. Rather than prices adjusting to attain equilibrium, the main story is one of quantity adjustment allowing recessions and possible attainment of underemployment equilibrium.