the rate of growth of . This is determined by (the ratio of net fixed investment or saving to ) and . A country might, for example, save and invest 12% of its national income, and then if the capital coefficient is 4:1 (i.e. $4 billion must be invested to increase the national income by 1 billion) the rate of growth of the national income might be 3% annually. However, as Keynesian economics points out, savings do not automatically mean investment (as liquid funds may be hoarded for example). Investment may also not be investment in fixed capital (see above). Assuming that the turnover of total production capital invested remains constant, the proportion of total investment which just maintains the stock of total capital, rather than enlarging it, will typically increase as the total stock increases. The growth rate of incomes and net new investments must then also increase, in order to accelerate the growth of the capital stock. Simply put, the bigger capital grows, the more capital it takes to keep it growing and the more markets must expand. The Harrodian model has a problem of unstable static equilibrium, since if the growth rate is not equal to the Harrodian warranted rate, the production will tend to extreme points (infinite or zero production). The Neo-Kaleckians models do not suffer from the Harrodian instability but fails to deliver a convergence dynamic of the effective capacity utilization to the planned capacity utilization. For its turn, the model of the Sraffian Supermultiplier grants a static stable equilibrium and a convergence to the planned capacity utilization. The Sraffian Supermultiplier model diverges from the Harrodian model since it takes the investment as induced and not as autonomous. The autonomous components in this model are the Autonomous Non-Capacity Creating Expenditures, such as exports, credit led consumption and public spending. The growth rate of these expenditures determines the long run rate of capital accumulation and product growth. Marxist concept Marx borrowed the idea of capital accumulation or the concentration of capital from early socialist writers such as Charles Fourier, Louis Blanc, Victor Considerant, and Constantin Pecqueur. In Karl Marx's critique of political economy, capital accumulation is the operation whereby profits are reinvested into the economy, increasing the total quantity of capital. Capital was understood by Marx to be expanding value, that is, in other terms, as a sum of capital, usually expressed in money, that is