In just about every project we've been involved in, we've had to focus the projects on the highest-need and highest-risk individuals. If that is an early childhood intervention, you want to find the neighbourhoods where the most people are not showing up to kindergarten ready for school, and focus resources there. Or if it's a recidivism project, you want to find the folks who have the highest risk of going back.
It's often the case that if you just take the entire population you could potentially serve and try to design a project around that, it just doesn't work in terms of the economics. You really have to be very focused on identifying the highest-need individuals.