In his inauguration address last week, Mayor Mitch Landrieu touted a dramatic decrease in homicides: “In 2010, New Orleans was America’s murder capital. But no more — murder is at a historic near-30-year low.”

He’s said this before, but we haven’t seen anyone check to see if it’s true. So we did.

There are three assertions in the mayor’ 20-word statement:

• New Orleans was the country’s “murder capital” in 2010.

• It no longer is.

• “Murder” is at a near 30-year low.

It seems straightforward, but the reality is complicated. For instance, New Orleans was the “murder capital” among cities larger than 250,000 people — but not for cities larger than 100,000 people.

And while the number of homicides is the lowest in almost 30 years, the homicide rate isn’t. The rate — the number of homicides divided by the population — is how you can compare cities of different sizes.

The mayor went from one fact based on the homicide rate — New Orleans was the “murder capital” — to another based on raw numbers. People listening to his speech, unlikely to know this, may take Landrieu’s statement to mean that the city’s homicide rate is at a low not seen in almost 30 years. It’s not — although it is the lowest since 1999.

Here’s what we found.

Was New Orleans the country’s murder capital in 2010?

There is no official “murder capital” in the U.S. The FBI’s Uniform Crime Reporting Program, which provides annual statistics on major crimes, does not rank cities.

Rankings are done by different people, often journalists, based on their own standards. Some look at all cities with more than 100,000 people; others restrict their list to those above 250,000 or even a million.

Although many have said New Orleans was the “murder capital” in 2010, that’s not true if you look at all cities larger than 100,000 people. Flint, Mich., with a population of 102,000, held that distinction that year and still does. New Orleans was second.

But among cities with a population above 250,000, New Orleans had the highest homicide rate in 2010 and 2011.

In 2010, with an official Census population of 343,000 and 175 homicides, New Orleans had about 51 homicides per 100,000 people. That went up to 55 per 100,000 in 2011, when the city had about 360,000 people and reported 200 homicides.

Either way, the “murder capital” is based on the homicide rate, not the sheer number of killings. Other cities, such as Chicago and New York, had many more killings than New Orleans in 2010.

For example, New York City posted the country’s highest number of homicides in 2010, with 536, but because its population was about 8.2 million, its homicide rate was 6.5 per 100,000 people. Chicago has led the country for the last few years in the sheer number of killings — between 400 and 500 per year. But its homicide rate has consistently been below 20 per 100,000 people.

Landrieu’s statement about New Orleans being the “murder capital” in 2010 is true if you look at the largest cities in the country; it’s not if you include smaller cities as well.

Murder capital no more?

By 2012, New Orleans’ estimated population had grown to 370,000. Homicides dropped slightly, to 193. With more people and fewer killings, the rate dropped to 52 per 100,000 residents.

Meanwhile, the opposite was happening in Detroit: Killings were on the rise and the population was shrinking. Its homicide rate in 2012 was 55 per 100,000.

That year, Detroit had the highest rate among major cities and New Orleans dropped to No. 2.

Last year, with 156 killings in New Orleans and an estimated population of about 378,000, the city had a homicide rate of 41 per 100,000.

That was second-highest in the country among cities with populations of at least 250,000, and third-highest for cities with populations of at least 100,000.

Either way you look at it, Landrieu is right: We’re no longer No. 1.

‘Murder is at a historic near-30-year low’

This is where it gets complicated, because we’re no longer talking about homicide rates.

Last year, New Orleans had 156 homicides, which is indeed the fewest since 1985, when there were 152.

However, the homicide rate — killings measured by population — was not at a 28-year low. It is at a 14-year low — the lowest since 1999. That year, the rate was 34 per 100,000.

Mayor cites rate in one case, number in another

156Homicides in New Orleans in 201328Years since city had that few homicides

41New Orleans homicide rate in 2013 (per 100,000 people)14Years since homicide rate was that low

Landrieu said in his speech, “In 2010, New Orleans was America’s murder capital. But no more — murder is at a historic near-30-year low.”

In doing so, he first referred to the murder rate and then to raw numbers. The average listener wouldn’t know that the two were measured differently — especially because the mayor simply referred to “murder” being at a historic low, not the number of murders.

Although New Orleans’ homicide rate made it the “murder capital” among major cities in 2010, the rate is not at a “near 30-year-low.” It is at a 14-year low.

That is progress, but it’s not as historic as the mayor portrayed.

The city’s homicide numbers do appear to be moving in the right direction. And each part of Landrieu’s statement is arguably true. But in combining them and not being clear about what he was talking about, Landrieu made it easy for people to come away with the mistaken impression that the homicide rate is the lowest in almost 30 years.