During presidential campaigns, it’s not unusual to hear candidates say they will focus on strengthening the nation’s economy. But once in the White House, which presidents have truly delivered on that promise?

When it comes to shoring up the nation’s economy, Franklin D. Roosevelt, Warren G. Harding, and Rutherford B. Hayes top the list, while William Henry Harrison, Herbert Hoover, and Martin Van Buren rank at the bottom, according to a new study by the Georgia Institute of Technology.

The first-of-its-kind study analyzed up to 220 years of data to estimate an economic “grade point average” for presidents who served from 1789 until 2009.  The research, conducted by Mark Zachary Taylor, assistant professor in The Sam Nunn School of International Affairs, Ivan Allen College, appears in the October edition of P.S. Political Science & Politics.

On Taylor’s report card, William McKinley and Millard Filmore round out the top five, and founding fathers George Washington and John Adams are still on the honor roll with a grade of A-. Notable presidents like Harry Truman and John F. Kennedy rank slightly lower in the A-/B+range. Bill Clinton and Ronald Reagan are the best-rated recent presidents earning a grade of B.

Most existing presidential ranking systems tend to be clouded by partisan bias, subjective judgments and other aspect of presidential performance, Taylor said. This economic ranking system is based on objective, statistical data and is meant to be a serious way to gauge presidential economic performance.

“Put simply, if ‘It’s the economy, stupid,’ then we need to make stronger efforts to properly judge economic performance and to assign credit and blame where they are most deserved,” Taylor said. “These rankings are meant to constitute a scientific step in this direction.”

Taylor analyzed up to 220 years of data from the Measuring Worth Project at the University of Illinois at Chicago. He then graded the presidents individually using the traditional A-F (4-0 point) scale based on how well each performed in eight economic areas. Taylor used multiple and competing statistical measurements, ranking algorithms and time lags to ensure the data was unbiased. No historical or ethical judgments were used to adjust the findings.

Taylor’s objective approach yielded some surprises, such as the high ranking of presidents who traditionally have been poorly regarded like Harding, Hayes, and Fillmore. Also some national heroes – Abraham Lincoln, James Madison, John Quincy Adams, and Andrew Jackson – receive D's for poor economic performance.

“It makes sense when you dig into the history,” Taylor said. “In the case of Lincoln, to fight a war, you have to print money and go into debt. That’s bad for the economy in the long run, but sometimes there are more important things than the economy, such as staying together as one nation.”

Taylor also found correlations between the characteristics of presidents and their economic performance. For example, presidents who have been good for the U.S. economy tend to belong to pro-business political parties, work with a Congress in which only one house is dominated by their same party, serve during wartime and were raised in middle-class environments.

Presidents with below average economic performance often belong to parties that are relatively pro-farmer, pro-laborer, or pro-consumer. They tend to enter a single-party federal government in which one congressional house flipped parties, and they typically were raised in lower-class environments, the research shows.

Interestingly, presidential economic performance did not correlate with the person’s pre-political career, birth order, historical “greatness,” or whether he was a “dark horse” versus a well-vetted president, Taylor said.

Taylor cautions that these findings refer to the past performance of a group and cannot be applied to the 2012 election to predict whether Republican nominee Mitt Romney or U.S. President Barack Obama would be better for the economy. The study also did not include President Obama’s first term because it is not completed and the data will not be available until 2015, Taylor said.

What the research does suggest is that a president can affect the economy, even though the executive branch may appear on paper to have a limited role.

“It is tempting to dismiss these rankings as the product of dumb luck: getting elected at the top or bottom of the business cycle,” Taylor said. “Randomness surely plays some role in these rankings but presidents also bear responsibility for making their own luck.”