Click on a checkbox to turn on an indicator. The circles on the threshold bar indicate the national benchmark and either the national minimum (all the way to the left) or national maximum (all the way to the right). The areas that are colored in on the map fall between these two values.
Click and drag on the sliding circles to adjust these values. When more than one indicator is turned on, counties will be darker where more indicators overlap.
To fine-tune the threshold on the slider, click the slider circle with your mouse and then use the arrow keys on your keyboard to move the slider circle up and down the threshold bar.