Following are the reasons for increase in size and growth of population :

• Child marriage : People in the state of Rajasthan get married at a a very early age. Consequently, they have children at an early age, hence the population increases. Legal age for marriage is 21 and 18 years for boys and girls respectively. 
• Poverty and low standard of living : Since ancient times, Rajasthan has been economically backward. Population is used both as a power and means. Therefore, people wanted to increase population both for power and means. Due to this, population increased rapidly. In current time, people of lower sections treat an additional child as an additional source of income.
• Lack of education : The standard of education in Rajasthan has been low. Due to illiteracy, people are not aware of their future. The conditions of female literacy is miserable in comparison to male literacy in Rajasthan. 
• Economic backwardness : Along with economic development, the population growth declines. Rajasthan is backward from the point of view of economic development. 
• Hot climate : Due to hot climate, people get mature early, due to which population growth rate increases.
• Failure of family planning programs : Lack of desire among people, carelessness of the employees and inadequate awareness towards the programs of family planning are the main reasons for no decline in population growth rate. 
• Difference in birth and death rate : The population growth in Rajasthan remains very high due to huge difference in birth rate and death rate. As per the economic survey of 2014-15, the birthrate per 1000 in 2012 was 25.9 ,and at all India level, it was 21.6. Compulsion of marriage and less age at the time of marriage is the major reason for this. 
• Population migration : In the planning phase, lot of people from neighbouring countries as well as other states migrated to Rajasthan.