Most event professionals know the mood of the room.

They take in the reaction of the crowd, have conversations afterward, and don’t delay on the ever-important post-event survey.

In the end, they understand how the audience felt when the lights came back on.

But here’s something many don’t know: what’s the mindset of those who didn’t make it to the event? What caused those who didn’t show up to take a pass?

It’s important knowledge — for obvious reasons. If you understand why people decline you can change the experience that you are offering and, next time, change their minds.

Here are some strategies you can use to understand and convert the no-shows.

Look to Content First

Of course, there are many reasons people don’t attend events.

Often, there are scheduling conflicts that simply can’t be overcome. Every audience member has obligations. But if you take care of basics — schedule well, keep people comfortable, and market properly in advance — then you have to look to content as the reason some decline.

People generally attend events for one of two reasons: they need the information you are providing or they wantto see your program.

Either experience, done properly, can fill a room with enthusiastic guests.

For example, a tax attorney may need to hear about the practical impact of the Tax Cuts and Jobs Act. A credit market analyst may need to hear what a former Fed chair has to say about interest rates. Content that truly fills an audience need will always fill seats.

Desire is also just as powerful — as anyone who has ever stood through a concert can attest. For the right experience, people will clear their calendar, pay to get in, stand for 90 minutes and line up afterward to meet the person on stage.

True, these experiences are rare. But many of us can name a handful from personal experience. There’s power in FOMO, the “fear of missing out.”

When people flake on events, chances are the experience failed to meet one of these two criteria. They didn’t need or want to be there badly enough, and the date was carried by other priorities.

Listen to the Audience

Ask yourself this tough question: which scenario describes your program? Does your audience need the information or perspective you are conveying? Or do they badly want the experience you provide?

If the answer is muddy, there’s plenty you can do.

Start by listening. Learning the information your audience needs and the experiences they want is powerful mojo, and you don’t need magic to get it. You simply have to ask.

Just as you survey audience members after an event to gauge satisfaction, you can and should collect input before beginning your planning process. Audience input should be a primary ingredient.

How you obtain it will depend on the norms in your industry and the culture of your organization, but here are some simple and cost-effective tools.

With a free MailChimp account and some minimal effort, for example, you can survey your audience about what they need and want before you start to plan.

Spend some time on the questions, creating data that will help you frame programming and plan an experience. Keep it tight, and be sure to include at least one opportunity for respondents to comment freely. That text box can provide gold.

A few good phone conversations can also yield a great deal of understanding, and many people will be flattered by the opportunity. Select a diverse group and schedule some calls. The same rules apply: create a tight and thoughtful script. But don’t be too rigid. It should be a conversation, not a poll, and tangents can be fruitful.

If your organization supports it, have a small group of audience members into the office for breakfast and a conversation. What separates this from interviews is the group dynamic. A focus group can often be extremely creative. They can also fall prey to group-think.

Challenge your guests, but keep it light. Have one staffer on hand to converse and another to take notes, but don’t fill the room with your personnel. It can stifle conversation.

Note Who’s Not Coming

Here’s another exercise that may be worthwhile. Go back to the events you did last year and focus on those who did not attend. Look at who was invited, who RSVP’d and who was actually in the room. Create lists of the people who declined and those who flaked.

Are there any commonalities? Did you fail to attract young people? C-suite executives? People from out of state? Look for common threads that indicate the segments you didn’t attract.

Then, talk to them using a survey or interviews — or both.

This is a tougher task, because many may be reluctant to discuss an event they missed. Ask about the events they do attend, what draws them, and what you can do to warrant their time and attention.

Keep it short and free of judgment. Those who participate — and the pool may be small –will almost certainly offer valuable information.

Remember, the best marketers study their customers and prospects obsessively — and that includes the ones who got away.