Here's a quick quiz: What is the only form of motor sports--in fact, one of the only sports period--with higher year-over-year metrics, both in attendance and in television and digital consumption?

Nope, not IndyCar. Not Formula 1. Not MotoGP. And not the NFL or the NBA.

Sports-car racing is the best sports-business success story hiding in plain sight: IMSA, the premier sanctioning body for sports-car competition in North America. IMSA currently sanctions seven different series that include 14 manufacturers (Porsche, Ferrari, Chevrolet, Ford, Audi, BMW, Mercedes, etc.)

Under its TV deal with Fox Sports, ratings are up dramatically. And track attendance is at an all-time high; this year's Daytona attendance set an all-time record, and Sebring saw its largest crowds since 2006.

In a world of sports consumption where flat is the new up, IMSA is actually up.

And speaking of "up," 2018 will see the full-time addition of Team Penske to the IMSA WeatherTech SportsCar Championship series. (Any time Roger Penske enters a racing series--or an industry--you know opportunities must exist.) Team Penske debuts this weekend at the season finale--Motul Petit Le Mans--in preparation for the team's full-season campaign next year. (The race will be broadcast live on FS1 beginning at 10:30 a.m. ET Saturday, with Nascar legend Jeff Gordon in the booth for FS1 to call the start of the race.)

So how has IMSA managed grow during a period when other sports--and many other forms of entertainment--have suffered dips in viewership and attendance?

To find out--and to learn more about how to navigate the choppy waters of not just a merger but also a major business transition--I talked with IMSA president Scott Atherton. Scott has overseen major changes in the sport, including the merger of two separate series with two distinct cultures and personalities.

Haden: To the casual observer, the last few years could seem like an overnight success story.

Atherton: It's an overnight success story that's been 17 years in the making. [Laughs.]

A fundamental catalyst occurred four years ago: Merging what was the Grand-Am Series and the American Le Mans Series into one. The vision and foresight and confidence Jim France had in doing that...well, it was definitely seen as a high-risk move at the time.

When the merger was announced, there was at best cautious optimism. Four years later, Jim looks pretty darned smart. That's the broad stroke answer.

So why did the merger work? Often, two entities come together and become less than the sum of their parts.

For starters, it truly was a merger. It wasn't an acquisition dressed up as a merger.

Then we went through an extensive process of adopting best practices, and not just on the racetrack. We took a deep dive into Le Mans, Grand-Am, Nascar...and whenever possible, the best practice was adopted.

That meant egos had to be put aside, and quite frankly, some people didn't make the cut for just that reason.

We relocated all those resources into our headquarters in Daytona Beach [Florida]--and, for the first time, the majority of the key management were also under one roof. That not only combined the assets of the two entities but also gave us access to all the resources and capabilities of what we call the "mothership": Nascar. (Jim France, son of Nascar founder Bill France, Sr., is the chairman of IMSA.)

In some parts of our paddock those are fighting words, because Nascar is its own entity. Stock-car racing is clearly a mainstream sport...but it's not sports-car racing, which has its own culture, one that definitely deserves respect.

Merging two organizations is hard enough, but then throw in oversight from an even larger organization....

Jim provided resources, but not in a heavy-handed or oppressive way. We didn't Nascar-ize sports-car racing. Instead, we helped the series thrive by giving it sustainability and access to resources it had never had.

Not only could we tap into their capabilities in marketing, research, risk management, etc., but we also had access to "dry" subjects like HR, accounting...all the things that are important to building a sustainable business.

The other reason why it has worked this way is we made a commitment to every team. We said whatever equipment you are currently racing with, we'll make sure you have an appropriate runway where your "stuff" will be viable and competitive...and we won't move the goalposts on you.

Teams make huge investments in equipment, and we wanted them to have a high degree of confidence in our commitment to technical details, and to what would be allowed. We also laid down a vision that saw us through that transitional period with a long list of compromises. One of those compromises needed to allow a Daytona prototype car to compete with an Le Mans prototype.

I know enough about the cars to think that sounds impossible.

Lots of people agreed with you. [Laughs.] There was a high degree of skepticism. Industry experts said that sounded great in theory but in practice would be impossible.

To the credit of our tech and engineering teams, they achieved it.

On any given weekend, a Daytona prototype or a Le Mans prototype could win the race.

That period of compromise and allowing existing equipment to compete came to an end for GT in 2015 and prototypes in 2016. This was the first year we had purpose-built, modern-spec cars in all of our racing classes that weren't compromised versions.

And now, we're proud to say the quantity and quality of our starting grids speak for themselves.

Plenty of people say one of the toughest leadership challenges is making a merger work not just for those outside the organization, but inside.

In some ways, this was the most difficult transitional process I've ever gone through. Personnel, practices, procedures, cultures...ask anyone who came from a Grand-Am or Le Mans background and they would probably agree. [Laughs.]

It was anything but easy. The process stretched business relationships, friendships, marriages...looking back, once you've achieved a goal, the process doesn't seem nearly so bad.

As you're working through things it's easy for people to find fault and see weakness and shortcomings. That's natural. Hang in there, work as hard as you can...because when some of your changes start to come through, and people start to be pleasantly surprised...some of those early concerns will turn into people saying, "Hey, these guys are onto something."

That also made this one of the most enjoyable experiences I've ever had.

You also pulled off some major partnerships, which had to give stakeholders confidence in the future.

You're right. When we announced the merger we also announced a five-year TV deal with Fox. To have a five-year term with a TV partner was an unprecedented luxury in our space, especially one with a network as powerful as Fox.

The other significant development was the fact we could announce a major non-endemic mainstream title partner. WeatherTech had come to us and said, "We don't do small, we don't do typical. It has to be bold and unique. Until you have that opportunity, don't call us, we'll call you."

So with the blessing of Tudor, our former title sponsor--and a brand that is still with us today--we sat down with David MacNeil, the founder of WeatherTech, and presented our plan.

It was the briefest courtship we've ever been a part of. And it aligns us with one of the most prolific mainstream marketing partners anyone could ask for. WeatherTech is everywhere: magazines, TV, radio, outdoor...they're into everything. And they use us in much of their mainstream primary marketing, and typically in a premium way. That's another tent pole in answering the question of what enabled this to happen.

One thing first-time fans are struck by is that many of the cars look like cars they drove to the track...in a hyper-realized way, of course.

That's another over-arching umbrella: relevance. Our motorsports platform represents the most relevant opportunity for manufacturers to race what they sell.

Not just in the automobiles, though. With our prototypes, it's racing technology that has a direct link back to the production car. Prototypes are purpose-built, but GT cars are production cars that started their journey as a vehicle coming down the assembly line in a factory--then they get modified for performance and safety.

A Corvette, a Porsche, a Ferrari, a BMW...those cars don't just look the part, that's what they actually are.

From a manufacturer's perspective, they can develop technology on the racetrack with a direct line back to the showroom floor.

Speaking of dealer showrooms, dealers have to love seeing the car corrals at the tracks.

In the GT category, the cars and teams are definitely impressive, but what's almost equally impressive are the car corrals filled with fans who have driven their personal vehicles to the track.

They're not just fans. They're brand disciples. They love their cars and they love the brand.

That creates a friendly rivalry that goes beyond cheering for a particular team or driver. That makes the fans more invested in the sport...and also makes the manufacturers more invested in the sport. It really does work both ways.

Add all that up and it's great, but we're doing our best not to read our own press releases and just stay focused on building the value and sustainability of our championships.

Let's talk about sustainability. What do you see as your biggest challenges in the years ahead?

One challenge is the light-speed evolution of broadcast media as we know it: live streaming, startup media outlets, as well as the cornerstone networks and cable partners. Navigating the next generation and the next contractual period is job one.

Equal to that, though, is managing the rapidly advancing level of sophistication and professionalism of the teams and manufacturers. We've been fortunate to have top-level teams, but the new teams coming in definitely raise the bar. There's an unprecedented level of pressure on all facets of our competition: rules, regulations, competition, etc.

Keeping the welcome mat out, not just figuratively but with real substance, for our independent teams is extremely important. We've always had a mix of professional teams and drivers with independent teams that are pro-am combinations. That gives people the opportunity to race at the highest level of the sport, and we don't want to lose that, but when you add new top teams...making sure that you have an equally attractive environment for pro-am independent teams is a challenge we're up to--but it's easier said than done.

The pro-am teams also serve as the cultural bedrock of the sport.

The fact we have 14 manufacturers actively involved is outstanding and unprecedented, but racing is cyclical, and historically, manufacturers occasionally come and go. Year in and year out, the independent, pro-am teams are the fabric and history of the sport.

We don't ever want to get away from that.

Then factor in that the manufacturers don't just race; they're fully engaged in every aspect of our business. Each has made a full-time, significant investment in track activation, support with mainstream marketing...they sign a detailed agreement that requires their active participation on and off the track.

Combine that with the history and legacy of our pro-am teams...and that means everyone is a stakeholder--not just in name, but in actuality.