There are four distinct Phases of Population Growth identified in this period : 

Phase I :

The period from 1901-1921 is referred to as a period of stagnant or stationary phase of growth of India’s population, since in this period growth rate was very low, even recording a negative growth rate during 1911-1921. Both the birth rate and death rate were high keeping the rate of increase low. Poor health and medical services, illiteracy of people at large and inefficient distribution system of food and other basic necessities were largely responsible for a high birth and death rates in this period.

Phase II :

The decades 1921-1951 are referred to as the period of steady population growth. An overall improvement in health and sanitation throughout the country brought down the mortality rate. At the same time better transport and communication system improved distribution system. The crude birth rate remained high in this period leading to higher growth rate than the previous phase. This is impressive at the backdrop of Great Economic Depression, 1920s and World War II.

Phase III :

The decades 1951-1981 are referred to as the period of population explosion in India, which was caused by a rapid fall in the mortality rate but a highfertility rate of population in the country. The average annual growth rate was as high as 2.2 per cent. It is in this period, after the Independence, that developmental activities were introduced through a centralised planning process and economy started showing up ensuring the improvement of living condition of people at large. Consequently, there was a high natural increase and higher growth rate. Besides, increased international migration bringing in Tibetans, Bangladeshis, Nepalies and even people from Pakistan contributed to the high growth rate.

Phase IV :

In the post 1981 till present, the growth rate of country’s population though remained high, has started slowing down gradually. A downward trend of crude birth rate is held responsible for such a population growth. This was, in turn, affected by an increase in the mean age at marriage, improved quality of life particularly education of females in the country. The growth rate of population is, however, still high in the country, and it has been projected by World Development Report that population of India will touch 1,350 million by 2025. 

Regional Variation in Population Growth :

The growth rate of population during 1991-2001 in Indian States and Union Territories shows very obvious pattern. The States like Kerala, Karnataka, Tamil Nadu, Andhra Pradesh, Odisha, Puducherry, and Goa show a low rate of growth not exceeding 20 per cent over the decade. Kerala registered the lowest growth rate (9.4) not only in this group of states but also in the country as a whole. A continuous belt of states from west to east in the north-west, north, and north central parts of the country has relatively high growth rate than the southern states. It is in this belt comprising Gujarat, Maharashtra, Rajasthan, Punjab, Haryana, Uttar Pradesh, Uttarakhand, Madhya Pradesh, Sikkim, Assam, West Bengal, Bihar, Chhattisgarh, and Jharkhand, the growth rate on the average remained 20-25 per cent. During 2001-2011, the growth rates of almost all States and Union Territories have registered a lower figure compared to the previous decade, namely, 1991-2001.

The percentage decadal growth rates of the six most populous States, namely, Uttar Pradesh, Maharashtra, Bihar, West Bengal, Andhra Pradesh and Madhya Pradesh have all fallen during 2001-2011 compared to 1991-2001, the fall being the lowest for Andhra Pradesh (3.5% percentage points) and highest for Maharashtra (6.7 percentage points). Tamil Nadu (3.9 percentage points) and Puducherry (7.1 percentage points) have registered some increase during 2001-2011 over the previous decade.

An important aspect of population growth in India is the growth of its adolescents. At present the share of adolescents i.e., up to the age group of 10-19 years is about 20.9 per cent (2011), among which male adolescents constitute 52.7 per cent and female adolescents constitute 47.3 per cent. The adolescent population, though, regarded as the youthful population having high potentials, but at the same time they are quite vulnerable if not guided and channelised properly. There are many challenges for the society as far as these adolescents are concerned, some of which are lower age at marriage, illiteracy – particularly female illiteracy, school dropouts, low intake of nutrients, high rate of maternal mortality of adolescent mothers, high rates of HIV/AIDS infections, physical and mental disability or retardedness, drug abuse and alcoholism, juvenile delinquency and commitence of crimes, etc.In view of these, the Government of India has undertaken certain policies to impart proper education to the adolescent groups so that their talents are better channelised and properly utilised. The National Youth Policy is one example which has been designed to look into the overall development of our large youth and adolescent population. The National Youth Policy of Government of India, launched in 2003, stresses on an all- round improvement of the youth and adolescents enabling them to shoulder responsibility towards constructive development of the country. It also aims at reinforcing the qualities of patriotism and responsible citizenship.

 Causes of Population Increase :

Rapidly increasing population of India is a result of prevailing high birth rates and a large decline in the death rate in our country. Thus analysis of factors which account for high birth rate and the factors that have contributed to a large decline inthe death rate is to be done.
The main causes for high birth rate are:

• The practice of early marriage is one of the main cause of the rapid increase in population. This gives wider reproductive period.
• Poverty of the masses in poor villagers is the another reason.
• India’s tropical climate making for earlier puberty, her joint family system, the institution of polygamy is also responsible for rapid growth of population.
• Lack of conscious family planning had also kept birth rate in India very high.
• The age and sex composition of the population and the fertility of women during the child-bearing age in India are most helpful for rapid growth of population. 

The main causes for decline in death rate are:

• Widespread and Improved medical and health facilities.
• Controlled spread of famines in India due to development of the means of transport and communications.
• Control on dreaded diseases like malaria and TB and diseases like small pox, chicken pox etc. have been completely eradicated.
• Improvements in hygiene in both rural and urban areas and supply of pure drinking water.
• Improvements in overall economic conditions of the masses have contributed to the sharp fall in the death rate.

It is clear from the above discussion that India is presently passing through a period of ‘Population Explosion’ due to her continuing high birth rate and a sharp decline in the deathrate. 

The Lancet: World population likely to shrink after mid-century, forecasting major shifts in global population and economic power :

By 2100, projected fertility rates in 183 of 195 countries will not be high enough to maintain current populations without liberal immigration policies.
World population forecasted to peak in 2064 at around 9.7 billion people and fall to 8.8 billion by century’s end, with 23 countries seeing populations shrink by more than 50%, including Japan, Thailand, Italy, and Spain.
Dramatic declines in working age-populations are predicted in countries such as India and China, which will hamper economic growth and lead to shifts in global powers.  Liberal immigration policies could help maintain population size and economic growth even as fertility falls. Authors warn response to population decline must not compromise progress on women’s freedom and reproductive rights. 

Improvements in access to modern contraception and the education of girls and women are generating widespread, sustained declines in fertility, and world population will likely peak in 2064 at around 9.7 billion, and then decline to about 8.8 billion by 2100—about 2 billion lower than some previous estimates , according to a new study published in The Lancet.
The modelling research uses data from the Global Burden of Disease Study 2017 to project future global, regional, and national population. Using novel methods for forecasting mortality, fertility, and migration, the researchers from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington’s School of Medicine estimate that by 2100, 183 of 195 countries will have total fertility rates (TFR), which represent the average number of children a woman delivers over her lifetime, below replacement level of 2.1 births per woman. This means that in these countries populations will decline unless low fertility is compensated by immigration. 
The new population forecasts contrast to projections of ‘continuing global growth’ by the United Nations Population Division , and highlight the huge challenges to economic growth of a shrinking workforce, the high burden on health and social support systems of an ageing population, and the impact on global power linked to shifts in world population.
The new study also predicts huge shifts in the global age structure, with an estimated 2.37 billion individuals over 65 years globally in 2100, compared with 1.7 billion under 20 years, underscoring the need for liberal immigration policies in countries with significantly declining working age populations.
“Continued global population growth through the century is no longer the most likely trajectory for the world’s population”, says IHME Director Dr. Christopher Murray, who led the research. “This study provides governments of all countries an opportunity to start rethinking their policies on migration, workforces and economic development to address the challenges presented by demographic change.” 

Accelerating decline in fertility worldwide :

The global TFR is predicted to steadily decline, from 2.37 in 2017 to 1.66 in 2100—well below the minimum rate (2.1) considered necessary to maintain population numbers (replacement level)— with rates falling to around 1.2 in Italy and Spain, and as low as 1.17 in Poland.
Even slight changes in TFR translate into large differences in population size in countries below the replacement level—increasing TFR by as little as 0.1 births per woman is equivalent to around 500 million more individuals on the planet in 2100.
Much of the anticipated fertility decline is predicted in high-fertility countries, particularly those in sub-Saharan Africa where rates are expected to fall below the replacement level for the first time—from an average 4.6 births per woman in 2017 to just 1.7 by 2100. In Niger, where the fertility rate was the highest in the world in 2017—with women giving birth to an average of seven children—the rate is projected to decline to around 1.8 by 2100.
Nevertheless, the population of sub-Saharan Africa is forecast to triple over the course of the century, from an estimated 1.03 billion in 2017 to 3.07 billion in 2100—as death rates decline and an increasing number of women enter reproductive age. North Africa and the Middle East is the only other region predicted to have a larger population in 2100 (978 million) than in 2017 (600 million).
Many of the fastest-shrinking populations will be in Asia and central and eastern Europe. Populations are expected to more than halve in 23 countries and territories, including Japan (from around 128 million people in 2017 to 60 million in 2100), Thailand (71 to 35 million), Spain (46 to 23 million), Italy (61 to 31 million), Portugal (11 to 5 million), and South Korea (53 to 27 million). An additional 34 countries are expected to have population declines of 25 to 50%, including China (1.4 billion in 2017 to 732 million in 2100; see table).
“This study is a thought-provoking contribution to the very lively, ongoing debate around the world’s demographic trajectory and its impact on our common future”, said Dr. Natalia Kanem, Executive Director of the United Nations Population Fund. “While the models, projections and time frames of different institutions may vary, all signs point towards declining global fertility. Protecting the reproductive rights and choices of women will be crucial in this demographic transition.” 

Declining working-age populations could see major shifts in size of economies : 

The study also examined the economic impact of fewer working-age adults for all countries in 2017. While China is set to replace the USA in 2035 with the largest total gross domestic product (GDP) globally, rapid population decline from 2050 onward will curtail economic growth. As a result, the USA is expected to reclaim the top spot by 2098, if immigration continues to sustain the US workforce .
Although numbers of working-age adults in India are projected to fall from 762 million in 2017 to around 578 million in 2100, it is expected to be one of the few – if only – major power in Asia to protect its working-age population over the century. It is expected to surpass China’s workforce population in the mid-2020s (where numbers of workers are estimated to decline from 950 million in 2017 to 357 million in 2100)—rising up the GDP rankings from 7th to 3rd.
Sub-Saharan Africa is likely to become an increasingly powerful continent on the geopolitical stage as its population rises. Nigeria is projected to be the only country among the world’s 10 most populated nations to see its working-age population grow over the course of the century (from 86 million in 2017 to 458 million in 2100), supporting rapid economic growth and its rise in GDP rankings from 23rd place in 2017 to 9th place in 2100 .
While the UK, Germany, and France are expected to remain in the top 10 for largest GDP worldwide at the turn of the century, Italy (from rank 9th in 2017 to 25th in 2100) and Spain (from 13th to 28th) are projected to fall down the rankings, reflecting much greater population decline.  

Liberal immigration could help sustain population size and economic growth 

The study also suggests that population decline could be offset by immigration, with countries that promote liberal immigration better able to maintain their population size and support economic growth, even in the face of declining fertility rates.
The model predicts that some countries with fertility lower than replacement level, such as the USA, Australia, and Canada, will probably maintain their working-age populations through net immigration (see appendix 2 section 4). Although the authors note that there is considerable uncertainty about these future trends.
“For high-income countries with below-replacement fertility rates, the best solutions for sustaining current population levels, economic growth, and geopolitical security are open immigration policies and social policies supportive of families having their desired number of children”, Murray says. “However, a very real danger exists that, in the face of declining population, some countries might consider policies that restrict access to reproductive health services, with potentially devastating consequences. It is imperative that women’s freedom and rights are at the top of every government’s development agenda.”  

India’s Population Trends: Lancet : 

According to a recent analysis by the Lancet, India’s population is forecasted to peak around 1.6 billion in 2048 from 1.38 billion in 2017. It will be followed by a 32% decline to around 1.09 billion in 2100. 

Key Points : 

• For the study, researchers used data from the Global Burden of Disease Study 2017.
• The Global Burden of Disease Study is a comprehensive regional and global assessment of mortality and disability from major diseases, injuries and risk factors.
• The study was initiated in the 1990s as a collaborative effort of hundreds of experts worldwide, including researchers at the World Health Organization (WHO), and the World Bank.
• Hampered Economic Growth: The study has predicted dramatic declines in working-age populations in countries such as India and China, which will hamper economic growth and lead to shifts in global powers.

India Specific Data:

• India in 2100 will be the world’s most populous country. The number of working-age adults aged 20-64 in India is projected to fall from around 762 million in 2017 to around 578 million in 2100.
• However, India has been forecasted to have the largest working-age population in the world by 2100. India is also expected to surpass China’s workforce population in the
• mid-2020s, where the working-age population is estimated to decline from 950 million in 2017 to 357 million in 2100.
• From 2017 to 2100, India is projected to rise up the rankings of countries with the largest total Gross Domestic Product (GDP) globally from 7 to 3 , in terms of nominal GDP.
• The country’s Total Fertility Rate (TFR) declined to below 2.1 in 2019 (data taken from the Global Burden of Disease Study 2017) and is projected to have a continued steep fertility decline until about 2040, reaching a TFR of 1.29
• in 2100.
• TFR indicates the average number of children expected to be born to a woman during her reproductive span of 15-49 years.
• India is also forecasted to have the second-largest net immigration in 2100, with an estimated half a million more people immigrating to India in 2100 than emigrating out.
• Given the trends of countries like the USA banning work visas and India being a developing country, has the potential to offer a huge manufacturing market to immigrants who want to work here.

Global Data:

• The world population is forecasted to peak at around 9.7 billion people in 2064 and fall to 8.8 billion by the century’s end, with 23 countries seeing populations shrink by more than 50%, including Japan, Thailand, Italy
• and Spain.
• By 2100, a total of 183 out of 195 countries will have TFR below the replacement level of 2.1 births per woman. The global TFR is predicted to steadily decline from 2.37 in 2017 to 1.66 in 2100, well below the
• minimum rate of 2.1. Replacement level fertility is the number of children needed to replace the parents, after accounting for fatalities, skewed sex ratio, infant mortality, etc. The population starts falling below this level.
• Huge shifts in the global age structure, with an estimated 2.37 billion individuals over 65 years globally in 2100 compared with the 703 million in 2019. 

Challenges :

• The new population forecasts are in contrast with projects of “continuing” global growth by the United Nations Population Division (UNPD).
• They highlight huge challenges to the economic growth of a shrinking workforce, the high burden on health and social support systems of an ageing population.
• As countries move toward prioritising development, fertility reduction is inevitable.
• At the same time, improved survival at all ages, especially at the older ages, would lead to the rapid ageing of the population. 

Suggestions : 

• Liberal migration policies could be adopted as a temporary solution for economic growth in the context of declining working population.
• Migrants contribute significantly to labour-market flexibility, innovation and technological progress, boost the working-age population and bring new skills contributing to the human capital development of receiving countries.
• It is more important to look for possibilities of investing in technological advancements that can compensate for human shortages.
• The effect of fertility decline on women’s reproductive health rights has to be accompanied by greater economic independence which would allow women to negotiate with the system on their own terms and for better support services as well.