South Dakota (left) and North Dakota (right), New Cases per Day. The dark red line is the rolling average.

Source: The COVID Tracking Project, September 3, 2020.

Last week, I went on in detail about the explosion of new coronavirus cases in the host state and bordering states subsequent to the Sturgis, South Dakota Motorcycle Rally. Across the United States, 17 states had increases of at least 10% in case rates over the last two weeks, including all those surrounding and including South Dakota.

Legend: South Dakota and the surrounding states with the increase in the rates of new cases over the past two weeks. South Dakota, Iowa and North Dakota ranked first, second and third, respectively among all states in terms of the highest rates of percent increases. For highest overall rates of new cases for this past week, Iowa, South Dakota and North Dakota ranked one, two, and three, as seen in the weekly graphs presented below.

Why this particular pattern? I doubt one explanation would cover everything, but the directions leading west (Montana and Wyoming) are sparsely populated. Interstate 90 passes through Sturgis and crosses east to where it connects to Interstate 29 near the Minnesota and Iowa borders.

Red States and Blue States: A Statistical Analysis. 

States have had different responses in how they have handled the COVID-19 pandemic. These differences include timing and degrees of closing and opening businesses and schools. They also include the attitudes and precautions taken by the individuals who inhabit the states. Finally, their governments make decisions as to whether to allow a mass infection event such as the Sturgis rally. 

Using the data for the week ending August 29th, I performed statistical analyses into whether Republican (red) states or Democratic (blue) states have more new coronavirus cases (per million population), more testing, or higher positivity rates. 

In my first analyses, I counted red states as those who voted for Donald Trump in 2016 and blue states as those who voted for Hillary Clinton. (Two states divided their votes according to Congressional district with Trump receiving the majority in Nebraska and Clinton the majority in Maine.) I performed a Wilcoxon ranksum test on the ranked figures.

Red states have a higher rate of new cases: p < 0.0001

Blue states have a higher rate of testing:  p = 0.176 (insufficient p value to support the statement)

Red states have a higher rate of positivity: p = 0.0015

Red states hold 17 out of 20 of the top positions in new case rates this past week. 

For my second analyses,I counted red states as those which have Republican governors and blue states as those which have Democratic governors. Again, I performed a Wilcoxon ranksum test on the ranked figures. Many of the state designations overlap with the above analysis, so it is not surprising the results were about the same.

Red states have a higher rate of new cases: p = 0.0035

Blue states have a higher rate of testing:  p = 0.332 (insufficient p-value to support the statement)

Red states have a higher rate of positivity: p = 0.0093

Weekly Case Rates 

This week presented without commentary.

Iowa

South Dakota

North Dakota

Alabama

Kansas

Mississippi

Tennessee

Georgia

Arkansas

Missouri

Hawaii

Oklahoma

Nebraska

Texas

Idaho

Indiana

North Carolina

North Carolina

Illinois

South Carolina

Louisiana

Kentucky

Florida

Minnesota

California

Montana

Wisconsin

Utah

Virginia

Alaska

Rhode Island

Maryland

Ohio

Michigan

District of Columbia

Arizona

Washington

Delaware

New Mexico

Wyoming

West Virginia

Massachusetts

Oregon

Colorado

Pennsylvania

Connecticut

New Jersey

New York

Maine

New Hampshire

Vermont