Introducing proportional symbol maps to NBC News
I pitched and designed this style of map for a colleague’s story. It was the first time that the desk had tried a proportional symbol map, but now we use it routinely, like for this cross-desk collaboration on Hispanic population change. I designed these maps with tooltips so readers can explore the discussed trend in their local county.
Moving away from the choropleth style
The NBC Data and Graphics desk typically defaults to choropleth maps for this type of story, but I decided to use a proportional symbol map for two reasons:
In a choropleth map the sprawling, sparsely populated counties prevalent in the West would dominate the map disproportionate to their story relevance.
The dual variate nature of the dot density map allows us to more accurately capture public health risk by highlighting the areas that both have low vaccination rates and large populations.
I created this map using d3.js. The article version is responsive and the desktop version has tooltips that appear when the reader hovers over a county (as demonstrated above).
Tools
QGIS and Python Geopandas for data prep and county centroid generation
d3.js for graphic and legend