How do you choose a font for extremely limited space, i.e. will fit the most READABLE text in the smallest space?

I often have very limited space when creating reports and dashboards for users. I usually use Arial, or Arial Narrow, but UI isn't my area of expertise, so I want to know, how do you determine an optimal font for fitting the most readable text in the smallest space?

Here is an example: Keep in mind this is just an example, as there are many times that space is limited, such as when you need to squeeze a million columns into a report, etc.