And the best 'quick' answer is this web overview (can't vouch for its accuracy - but it looks about right)
October, 19th 2013 Shanghai is China's most populous city and the largest city proper in the entire world. It's both a major financial center and a global city and sits at the mouth of the Yangtze River in the Yangtze River Delta of East China. Known as the Pearl of the Orient and the Paris of the East, Shanghai's population in 2013 is now estimated at 23.9 million, which means it has finally surpassed the entire population of nearby Taiwan.
Shanghai Population 2013
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The population of Shanghai is now estimated at 23.9 million in 2013, up from its 2012 population of 23,710,000. The city ranks first in China and the world in terms of population, and it has a population density of 3,700 people per square kilometer, or 9,700 people per square mile.
The city has a total area of 6,340.5 square kilometers (2,448 sq mi) and it is mostly flat, except for a few hills in the southwest region, and the average elevation is just 4 meters. Shanghai also has an extensive network of rivers, canals, lakes and streams, all of which combines to create a perfect setting for a large population.
Shanghai has been one of the fastest developing cities in the world for the last twenty years, with double-digit growth nearly every year since 1992, except during the global recession of 2008-2009.
Shanghai Demographics
According to the 2010 Census, Shanghai's population was 89.3% (20.6 million)urban and 10.7% (2.5 million) rural. More than 39% of Shanghai's residents are long-term migrants, a number that has tripled in ten years. Migrants are primarily from Anhui (29%), Jiangsu (16.8%), Henan (8.7%) and Sichuan (7.0%), while almost 80% are from rural areas. Interestingly, they have made up the largest percentage of the city's growth, as Shanghai's natural growth rate has been negative since 1993 because of low fertility rates.
Like most of China, the vast majority (98.8%) of Shanghai's residents are of Han (?) Chinese ethnicity, with only 1.2% belonging to minority groups. Still, the number of minorities in Shanghai has grown by an astounding 165.5% since 2000, which is faster than the population growth. Shanghai also has 150,000 officially registered foreigners, including 31,500 Japanese, 21,000 Americans and 20,700 Koreans. Of course, this is based on official figures, so the real number of foreign citizens in the city is probably much higher.
Shanghai has one of the highest life expectancies in the world, and the highest in mainland China, at 82.13 years.
Shanghai Population Growth
While some would believe that Shanghai has hit its peak population this is far from the truth. It's projected that Shanghai, along with Beijing, will have a population of more than 50 million by 2050, which is double the current level because of fast-paced urbanization in the region and strong economic growth.
China has become known around the world for its famous one-child policy, which has helped to keep the population in check. On the other hand, this has also contributed to a shrinking workforce in the area as well as a rapidly aging population. Migrants from the rural areas of the country are turning to Shanghai, though, and they will give the city the growth it's after. This migration to the area will fuel growth for decades to come, as Shanghai itself has had a negative natural growth rate for twenty years due to low fertility rates.
China is also testing reforms to its hokou system, which will offer incentives to migrants who move to rural people in the cities, providing them the same benefits as local residents. This should help to further Shanghai's growth in the coming years.
Officials also believe Shanghai will reach a minor peak in population in 2013 before climbing further, although the city still has a lot of demographic problems to overcome. This includes a very low fertility rate, an imbalance in the gender ratio (113 boys:100 girls) and an increasing age, which may become a burden as the city grows further.
Mr Schleicher, who runs the Pisa tests taken every three years, says Shanghai is engaged in a systematic, long-term project to improve education, as a way of transforming its economy.
"You can see from the minister down to the teacher in the classroom that this is their future and they believe education is the great equaliser," says Mr Schleicher, the OECD's education expert.
"That's why they make it prestigious to teach in a tough school," he says.