What is the best source of government data on the H1B program (e.g total visas per year, count by industry / job function, nationality of recipient counts)? Als

What is the best source of government data on the H1B program (e.g total visas per year, count by industry / job function, nationality of recipient counts)? Also, do you know of any original sources / documents which discuss the future of the program and how it will be assessed whether there is enough talent domestically in a given field of work. Thanks