Photo by: Robert Agthe.

Hilton (NYSE:HLT) is back in publicly traded hands after an IPO that priced the company at $19.7 billion. Blackstone (NYSE:BX) took the company private in 2007, worked on improving its operating metrics, and will now record a massive profit (Bloomberg estimates $8.5 billion) from the successful resale of Hilton Worldwide.

I've spent the morning digesting Hilton's S-1 filing with the SEC. Here are eight interesting things I found inside.

1. Hilton owns a fraction of its hotels.
Around the world, Hilton manages 3,843 hotels with 596,765 rooms. That's up some 39% since the company last reported earnings publicly in June 2007. It owns 4% of the hotels in its system.

2. It's the American hotel leader.
The company has 513,000 rooms under its umbrella in the United States, giving it 10% of market share, just slightly above its competitor, Mariott International (NASDAQ:MAR). When it comes to rooms under construction, Hilton comes in at No. 2, having control of 19.1% of all inventory in progress.

3. Hotel employees love unions.
In the business, risk is one big number: 27%. That's the percentage of Hilton's employees, and franchisee's employees who participate in collective bargaining for wages, salaries, and working conditions. If the hotel industry continues to improve on the back of an improving economy, union demands could compress profitability for its franchisees, and ultimately the corporate company.

4. China is a big growth market.
Since going private in 2007, Hilton has expanded aggressively in China. The company reports having 160 hotels in operation or under construction, up from just six hotels seven years ago.

5. Hilton hotels house 125 million people annually.
Through its owned and franchised properties, Hilton houses 125 million customer visits, more than any other company in the world.

6. Hotel occupancy is up considerably.
If there's one metric that matters in the hotel industry, it is occupancy. Hilton's occupancy rate has improved from 68.4% in 2010 to 72.3% in 2013.

7. Average rates are up big.
When occupancy goes up, so does pricing -- or at least that's what you'd want to see. Average daily rates have risen from $126 to more than $136 since 2010.

8. Efficiency is leading profitability.
Revenue per available room is a measure of average room rates and occupancy. When combined, you get revenue per available room, which measures how much the company generates from each room in its network. Since 2010, revenue per available room has rocketed, to $98.69, up from $86.16.

Will a hotel boom live on?
Hotels suffer from the pork cycle, an economic term describing a market where inventory (hotel rooms, in this case) goes from too little to too much. Over time, only the best operators can survive in a very competitive market like the hotel industry.

Luckily, Hilton has an excellent CEO at the helm. Christopher Nassetta was hand-picked by Blackstone to lead the company after going private. Since then, a series of efficiency improvements have helped drive profitability, but it will be up to the whims of competitors to decide the hotel industry's fate going forward -- will hotel chains refrain from making big investments in new inventory, driving down profitability? It's the billion-dollar question that will be answered over the coming weeks and months.

Fool contributor Jordan Wathen has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.