With this force, a build up of economic activity should lead to improved business sentiment, which, in turn, should lead to increased earnings and income. The rises in earnings and income should eventually encourage sustained growth in business fixed investment and personal consumption, respectively.
When the strength of the self-sustained recovery, or the momentum of this cyclical force, is very weak, there is a risk that private-sector activity might begin to decline, particularly if unable to absorb the negative impact of such exogenous factors as external demand and fiscal policy.