For most states in the U.S., last year ended on a strong note. But there are a few places in the U.S. that are struggling.

Recently released data from the Philadelphia Fed indicates that seven states -- North Dakota, Wyoming, Wisconsin, Illinois, Mississippi, Louisiana and Alaska -- likely saw their economies contract during the last three months of 2015.

The maps above and below show the Federal Reserve Bank of Philadelphia's state coincident index, which measures things like employment, hours worked in manufacturing and the unemployment rate to create an estimate of how economic growth has changed for each state over the past three months.

Essentially, the economy in states shown in light green is growing a little, while in states in dark green it is growing a lot. The economy in states in light red is shrinking a little, while in states in darker red it is shrinking more.

The animated gif below shows how the end of 2015 compares with the five years before:

As these maps show, the country is clearly doing far better in 2015 than it was in 2009, when most states were struggling. Yet in the years after 2009, the picture looks more mixed. The economy in Dec. 2015 doesn't look as strong as it did in Dec. 2014, when all states were seeing economic growth.

The main reason is historically low oil prices. The price of a barrel of Brent crude has fallen from over $100 in mid-2015 to less than $35 today. That is weighing on the economies of North Dakota, Wyoming, Alaska, Mississippi and Louisiana, which have extensive energy reserves and/or oil and gas refining facilities.

In Wisconsin and Illinois, fiscal issues and the sluggish performance of some manufacturing industries was likely to blame.

In total, 41 states saw their economies grow. The states with the strongest growth -- over 1 percent in the three-month period, according to the estimates -- include Oregon, Idaho, Arizona, Colorado, Kansas, Georgia, West Virginia, New Jersey and Maine. Michigan and Oklahoma weren't faring too well either at the end of 2015 -- the Philadelphia Fed's data shows that their economic growth was unchanged from three months before.

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