Census effect: City crime will ‘fewer’ next year

Most Indian cities will see a decrease in crime rates by 2027. This is a safe prediction. Historical precedent shows that crime rates in India’s major cities fall significantly in census years.This is not because of better policing, but because of a mathematical error – an error that the National Crime Records Bureau mentions in its fine print but is often omitted from reports based on its data.NCRB updates crime numbers every year. But for cities, it uses the population from the last census as the denominator in calculating crime rates. This population number remains unchanged until the next census. So while recorded crime rates may rise or fall each year, the number of people used to calculate crime rates remains the same – usually for ten years, but this time for more than 15 years.This is why comparisons like “crime rate in Delhi is rising” or “crime rate in Delhi is higher than in Mumbai” can be misleading unless the population base is understood.

Take Delhi for example. In the latest NCRB report, the population of Delhi city remained at Rs 16 crore as per the 2011 census. But the projected population of Delhi NCT is 22 crore. Since the city of Delhi occupies almost the entire NCT, if the NCT has a population of 22 million, it is obviously impossible for the city of Delhi to still have a population of only 16 million.This difference dramatically changes crime rates. The number of IPC crimes in Delhi and Delhi city is the same at 2,75,402. But since NCRB uses a different population base, Delhi’s crime rate is shown at 1,259 per one lakh people, while Delhi city’s crime rate is 1,688 per one lakh, which is 34 per cent higher.There is precedent for what happens when the population denominator is updated. The 2001 census showed that there were 35 cities in India with a population of more than 1 million.

After updating urban population data in 2011, 27 of these cities saw a decrease in crime rates. The rate in Kochi fell from 1,898 to 1,636 per one lakh population. Visakhapatnam, Bengaluru, Indore, Ahmedabad and Bhopal also recorded declines of more than 150 points. The sharpest “decline” occurs in rapidly growing cities, where older populations have become most obsolete.This is the census effect. NCRB uses the same city population until the next census as official city projections are not available.

NCRB calculations may slightly underestimate juvenile crime rates

A constant divisor makes interest rates appear to gradually inflate. When the census finally updates the population, crime rates are likely to have dropped significantly, even if the actual number of crimes has not dropped.Similar issues arise in other NCRB categories as well. According to the 2011 Census, the population under 18 years of age in India is 444 million rupees and the crime rate against children and juvenile crime rate. But with fertility rates falling, the United Nations estimates that the population under 18 is now around 433 million rupees. This means that juvenile crime and crime against children may be slightly underestimated in NCRB’s calculations.For older adults, the opposite may be true. NCRB used 2011 data on the elderly population – 104 million people aged 60 or above. But India is aging. The United Nations estimates that the number of people over 60 years old in India will reach 157 million in 2024. If so, NCRB may have greatly exaggerated crime rates against the elderly.Lesson: Crime numbers and crime rates don’t always tell the same story. The number of crimes is calculated annually. The ratio depends heavily on the population used in the denominator. During a census year, the denominator changes and crime rates seem to improve overnight.