Country Supply Quality: Welfare effect?

I think I saw someone say somewhere that the quality of the supplies in your "Country" can affect your welfare level. Is this true? Most guides say to set quality to 100 for country supplies (outdated, since 120 seems to be the lowest setting you can go for).

For players in the first months, and lower game levels we advise 120 (current minimum). It will cut your cost of health, education, gov. etc.

There will be an influence on the welfare index but it will kick in at higher game levels.
Currently there is no dependency. It will be added in May.

Where do you change this supply quality level and should you do it for corps aswell