I have always been curious over the number of developers in each country. Recently, out of a need to present this statistics for my work, I went deeper to search for an answer.
StackExchange provided me with data for a few countries. For example, US has a population of 300 million, and has 1 million programmers (that is 0.33%).
I took a lower figure and estimated that around 0.1% of a population are active developers who work on web/mobile. With that, I estimate the number of developers in each country as such:
| Country | Population | No. of developers (0.1%) |
| US | 300 mil | 300,000 |
| UK | 61 mil | 61,000 |
| Japan | 127 mil | 127,000 |
| Singapore | 5 mil | 5,000 |
| Hong Kong | 7 mil | 7,000 |
| Australia | 22 mil | 22,000 |
| China | 1,330 mil | 1,330,000 |
Quora also provided me a good answer, adding that around 10% of developers specialize in mobile development. That estimate does relate to the 40,000 iOS and 10,000 Android developers reported in appstorehq in 2010.