Academic references to outcomes theory: Duignan (2009d)*
Measuring them is really important.
But, it will not always be possible to measure all of them.
High-level outcomes are what the program is striving to achieve.
And just measuring a high-level, not-necessarily controllable indicator does not prove that you've changed it.
How not-necessarily controllable indicators look when they're mapped onto an outcomes model
* This particular reference can be cited to refer to the material on this page.