Crude Birth Rate (CBR) - Number of births over a given period divided by the person-years lived by the population over that period. It is expressed as number of births per 1,000 population.
Factors affecting birth rate:

• Government population policy, such as pronatalist or antinatalist policies (for instance, a tax on childlessness
• Availability of family planning services, such as birth control and sex education
• Availability and safety of abortion and the safety of childbirth
• Infant mortality rate: A family may have more children if a country's infant mortality rate is high, since it is likely some of those children will die.
• Existing age-sex structure
• Typical age of marriage
• Social and religious beliefs, especially in relation to contraception and abortion
• Industrialization: In a preindustrial agrarian economy, unskilled (or semiskilled) manual labor was needed for production; children can be viewed as an economic resource in developing countries, since they can earn money. As people
• require more training, parents tend to have fewer children and invest more resources in each child; the higher the level of technology, the lower the birth rate (the demographic-economic paradox).
• Economic prosperity or economic difficulty: In difficult economic times, couples delay (or decrease) childbearing.
• Poverty levels
• Urbanization
• Pension availability
• Conflict
• Illiteracy and unemployment

Interesting facts:

1. The birth rate is an issue of concern and policy for national governments. Some (including those of Italy and Malaysia) seek to increase the birth rate with financial incentives or provision of support services to new mothers. Conversely, other countries have policies to reduce the birth rate (for example, China's one-child policy). Measures such as improved information on birth control and its availability have achieved similar results in countries such as Iran.
2. TBirth rates vary within a geographic area. In Europe as of July 2011, Ireland's birth rate is 16.5 per 1000 (3.5 percent higher than the next-ranked country, the UK). France has a birth rate of 12.8 per thousand, while Sweden is at 12.3.