To map or not to map
Planned redundancy

Graphical forms impose assumptions on the data

In a comment to my previous post, reader Chris P. pointed me to the following set of maps, also from the New York Times crew, on the legalization of gay marriage in the U.S. (link)



(For those who did not click through, the orange colors represent two types of bans while the dark gray/grey color indicates legalization.)

These maps are pleasing to the eye for sure. By portraying every state as a same-sized square, the presentation avoids the usual areal distortion introduced by the map.

But not so quick. Note that each presentation makes its own assumption on the relative importance of states. The typical map scales weights according to geographical area while this presentation assumes that every state has equal weight. Another typical cartographic display uses squares of different sizes, based on the population of each state.

The location of states are necessarily distorted. One way to remedy this is to have hover-over state labels. On a browser, such interactivity works better than having to scroll to the top where there is a larger map which doubles as the legend.

It would be interesting to learn also about the future. Are there any legislation in the pipeline either to legalize gay marriage in the remaining orange states or to overturn the legalization laws in the gray states?


PS. [5/6/2015] Here is an alternative presentation of this data by David Mendoza.


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I made maps similar to these ones recently for a post on different methods of execution used in the U.S.

I like this type of presentation because it allows people to see the smaller states in the Northeast more easily. But as you wrote, in the NYT maps, it's hard to know which state is which because of the lack of labeling on the smaller versions.

Also I think the states could have been ordered better. South Dakota probably shouldn't be east of North Dakota. And West Virginia shouldn't be north of Virginia.

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