Data: I am looking for an API or dataset where I can find age distribution (age groups: percentage of an age group according to the population) and gender distributions for the biggest websites of each country like: Facebook (USA, Germany, France aso), Twitter (USA, Germany, France aso), Spiegel Online, Instagram aso. Something like Alexa Top 500 sites but with statistics about their audience.
Context: I am working on my Master's Thesis and would like to compare my scientific samples to the population.
Region: I need Data from the whole world.
License: Unfortunately I am a Student and can't spend more that 50 Euro on this data.
Format: A JSON API would be perfect. XML, CSV, XLSX or any other common data type is ok too.
Authority: I need the data to be reliable. That means, the sources of the data have to be visible and official.