This result has a disquieting economic meaning. In order to maintain the balance between capacity and demand over time, the rate of investment flow must grow precisely at the exponential rate ofps, along a path such as illustrated in Obviously, the larger will be the required rate of growth of investment, the larger the capacity-capital ratio and the marginal propensity to save happen to be. But at any rate once the values of p and s are known, the required growth path of investment becomes very rigidly set The razor's edge It now becomes relevant to ask what will happen if the actual rate of growth of investment --call that rate r--differs from he requirea rate psThis result has a disquieting economic meaning. In order to maintain the balance between capacity and demand over time, the rate of investment flow must grow precisely at the exponential rate of , along a path such as illustrated in Fig 1. Obviously, the larger will be the required rate of growth of investment, the larger the capacity-capital ratio and the marginal propensity to save happen to be. But at any rate, once the values of and s are known, the required growth path of investment becomes very rigidly set. s  The Razor's Edge It now becomes relevant to ask what will happen if the actual rate of growth of investment --call that rate r -- differs from the required rate . s