Podcasting is a $25 billion industry, and top podcasts have a lot in common — from length to number of episodes to cover art.

Now a new study by software company Podcastle pinpoints these similarities to help new and seasoned podcasters have a better shot at producing a successful show.

The U.S.-focused study used the Apple Podcasts charts to find the top podcasts and then studied a week’s worth of data, starting April 15. Podcastle also surveyed 1,000 podcast listeners to add to the findings.

The study found that “profit” is the main reason Americans want to start a podcast this year — and it can be a lucrative side hustle.

Related: 3 Secrets to Starting a Small Business Side Hustle That Gives Your Day Job a Run for Its Money, According to People Who Did Just That

Jannese Torres, the founder of the personal finance podcast, Yo Quiero Dinero, shared with CNBC earlier this month that she brings in an average of $37,394 monthly in revenue, partly through podcast ads. A June 2022 Bloomberg report revealed that some podcasters were making $18,000 a month with white noise.

Here’s what else the study showed about top podcasts and the listeners who tune in.

What Do Top Podcasts Have in Common?

The study found that the average length of a top 250 podcast was 65 minutes. Of those, 68% used the most popular format, an interview, while 20% used the second most popular format, a deep topic explanation.

The 10 most successful genres, in order, are society and culture, comedy and humor, true crime, news, education, business, health and wellness, improv, personal development, and documentary.

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The top 50 most successful podcasts had hosts that spoke an average of 174 words per minute, with an average of 58 filler words like “um” and “like” per episode.

Podcast intros for these top performers ranged from 30 to 59 seconds with half adding an ad to the intro.

Most of the top 50 podcasts (60%) had more than one host. Nearly three in four of the top 50 podcasts had at least one guest on the show.

For cover art, the top 50 had more black and blue colors in their cover art than any other color and 52% of the cover art didn’t have a picture of the host.

Though each podcast cover used a unique font, only 38% used bolded font.

Most people who want to start a podcast are motivated by potential earnings (34%) or by the avenue podcasting gives them to express their creativity (26%).

Related: This Flexible Side Hustle Is Helping Millions Earn Extra Cash — and Might Be ‘More Attractive’ Than an Office Job

Who Listens to Podcasts?

Podcast listeners have increased by nearly 70% since 2019 and there are more than three million active podcasts globally, according to Podcastle.

Most podcast listeners (64%) usually tune in on Spotify, with 34% choosing Apple Podcasts. A smaller percentage (6%) use YouTube Music.

The majority indicated that they returned to a show because the hosts or guests were entertaining (69%) and offered new information or perspectives (70%). A host’s expertise in a certain topic kept 36% of listeners coming back.

Most podcast listeners are doing something else while tuning in. Over one in four listeners (28%) were cooking or doing chores and more than one in five (22%) were commuting to work or school.

Listeners indicated that the biggest things podcast hosts should avoid are including too many ads or having poor audio quality. Too many ads turn off listeners across generations, with 70% of Americans citing it as their number one podcast turn-off overall.

Nearly half of all listeners surveyed said poor sound quality made them stop listening.

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