Personal and Community Finance / Economy

How Does Personal Economy and Finance affect Country / Community Economy?
Please elaborate. Technical terms are not necessary.

Well, a group's S/D functions are the sum of the S/D functions of the individuals comprising the group.

@clousems said in #2:
> Well, a group's S/D functions are the sum of the S/D functions of the individuals comprising the group.

What is S/D...?