Also something to consider is the SEO experts / consultants vs the manual labour... i see lots of potential in the Philippines for business process outsourcing ie: content writing, link building, etc...
The number of jobs related with SEO is now gradually increasing in the Philippines. Even the regional provinces apart from the metropolis now has more foreign investors looking to open up offices due to the low cost of living.
I don't know wich country has most SEO's But i know wich country has the most so called "seo experts" That's India ...
It really depends from the topics... In general, countries that have ENGLISH as their first language dominate.
Is there any SEO from Japan. I wonder if they really have good SEO.. Anyways, I think good SEOs are from US and Europe. There are many good ones from India but the numbers of bad ones are high.
As of my experience researching about SEO, there are lots of SEO Specialist in US, UK, India or Canada. I would also like to take note that there are growing numbers of SEO Experts here in Philippines, others who have been recognize by foreigner clients. There are lots of business process outsourcing from other countries here in Philippines specializing in SEO. You can check that by just looking on some website on job hunting in Manila, beating the IT or call center.
I don't know is there such statistic, but I think that this is the country with most residents - China.