In 1798, British economist and demographer Thomas Robert Malthus, published his' essay on population' in which he stated that:
1. Population increases in a geometric ratio (1,2,4,8....) where as the means which support it increases in an arithmetic ratio (1,2,3....)
2. After sometime there would be an imbalance in population growth and food supply.
3. When the imbalance reaches at a certain limit, some factors like hunger, epidemics, floods and earthquake etc. will bring the population at a desired level. Such a population "crash" is called catastrophic control of population. These factors were called positive checks by Malthus.