In maybe 10 years from now
Im certain sure that average in Bejing will be 179-181
And koreans in seoul average will little bit taller 180-182
Becasue there Value and richer .
They can buy good food with nutrient to serve their meeds and heightism value
This is inaccurate the average height in developed countries has risen since the beginning of the 20th centuray at a rate of about 1CM every decade. That increase slowed down in the 1980's to about a fifth of the speed. For example the swedish average of 20-29 year olds was 180CM in 1980 and 181CM in 2011. There is not enough data yet to say if that increase has stopped completely or continues to rise at a slow rate of about 1CM every 30-40 years.
Most statisticians agree that it won't go above 183CM at most but it's more probable that it stabilizes between 181-182CM. After that it may shrink or remain no one knows. The only country that hasn't experinced a slowdown in growth rate is the netherlands hence why they are the tallest nation on earth. However it is very unlikely that the average will exceed 185CM naturally as stature above that height is incresingly detremental to individual health.
If I had to guess I'd say most populations will reach an average of 177-183CM if given sufficient acess to health care and nutrition.
To put these numbers in a realistic context: Statistically an average of 181 mean that 97,8% of the population will be within 2 standard deviations (7CM) of the mean i.e roughly 98% of all swedes are below 195CM and 68,2% are between 176CM and 188CM. If I were 190CM I'd be taller or equal in height to about 9 out of 10 swedes.
So how tall is tall? I would say 85th percentile or "top 15%" which is about 187CM or more.