Producing content that will go viral can feel something like a crapshoot.

One week the blog post you dashed off in 15 minutes and hardly gave a second thought to lights up Twitter, while an in-depth analysis of industry trends you sweated over for hours sinks like a stone. If you're going to spend your precious time crafting content to attract attention to your business, you want to do better than hunches and hoping.

Luckily, there’s no shortage of data out there. Every day millions of posts, articles, and infographics are born into the world, and either avidly shared or pretty much ignored. To find out what falls into which category, the folks at BuzzSumo embarked on a truly massive data analysis project, combing through the number of social shares for a whopping 100 million pieces of content over eight months to find a far more scientific answer to the all important question, what makes content go viral? The result is a lengthy post jam packed with stats, charts, and tips. Here’s some of what they found.

Size Matters

You may have heard the common sense wisdom that with everyone being so busy these days, shorter is better when it comes to content. BuzzSumo heard it too. But it turns out the "short attention spans demand short content" theory isn't back by the numbers.

"We analyzed the top 10 percent most shared articles to see if this was the case. And according to our research, the opposite is true. On average, long-form content actually gets shared more than short-form content," reports BuzzSumo. "The longer the content, the more shares it gets, with 3,000 to 10,000 word pieces getting the most average shares (8,859 total average shares)." 

Narcissism Is a Powerful Motivator

Previous research has determined that content that evokes certain emotions like awe and anger is more likely to be shared. BuzzSumo's findings confirm this, but also add a corollary. People also love posts and quizzes that feed their ego. Narcissism, it turns out, is also a powerful motivator to share.

"People also share for selfish reasons, like narcissism. In fact, eight of the top 10 most shared articles in the past eight months were quizzes (seven from BuzzFeed, one from the New York Times). Why quizzes? Because when we share our quiz results, it fuels our identity and ego. Others will learn more about who we are, what we value, and our tastes," explains BuzzSumo.

Content Doesn’t Get Stale

Is it true that content needs to be fresh as the new blown snow to go viral? Not at all, according to BuzzSumo. While it's a fact that sharing falls off rapidly after your initial post, if you share again after some time has passed, the same content will again garner interest. Re-promoting older content actually pays.

"Don’t let your content be a one-hit wonder! Re-promote a post at least a week after it's been published. Alternatively, find old content that ties into an upcoming event/holiday, and re-promote that the day of the event," suggests BuzzSumo.

10 Is the Magic Number

It's no secret everyone loves lists, but it turns out we love lists of 10 things most of all. "10-item lists on average received the most social shares--on average 10,621 social shares. In fact, they had four times as many social shares on average than the second most popular list number: 23. The runner-ups were 23, 16, and 24," according to the BuzzSumo analysis. So if you’re planning a list, go long.

And Tuesday Is the Magic Day

Tuesday may seem like a pretty dull day, lacking the excitement of Friday, the freshness of Monday, and even the distinction of being "hump day," but apparently its very blah-ness means more folks are on the lookout for interesting content to brighten it up. "Generally content gets the most shares on Tuesday or Monday, depending on the social network," BuzzSumo found, noting that Facebook, Twitter and Google Plus favor Tuesday, while LinkedIn and Pinterest show more activity on Monday.