This is a Choropleth Map, a thematic map. A Choropleth Map shades in areas according to the measurement of the statistical data that is being depicted. In this map, the creator chose to split the positive values with the negative values by the use of different colors--pink shades for negative values and green shades for positive values. It should be noted that while a Choropleth Map can easily represent degrees of data visually, the representation on such a map can be "misleading" due to the size of a state. For example, a larger area (such as Texas) will likely have more of a visual impact on the viewer because of its size, but its size is unrelated to the data being displayed.
