Just as Billboard's music charts spell success for pop music, Apple's charts for the top paid, free and top-grossing apps have become a touchstone for the gaming industry, with a top ranking giving sales an extra boost.

As more mobile apps are downloaded around Christmas than at any other period, Apple freezes its charts as a way to deal with the overwhelming volume - giving top apps already on the lists guaranteed exposure over that period.

Game companies have double to 10 times the usual gamer traffic during this peak period, said Maria Alegre, chief executive of Chartboost, a mobile game ad network.

"But if you're in the top 5 or top 10 in the App Store rankings, then you get this extra exponential growth because everyone's looking at you," Alegre said.

The exact date and duration when Apple freezes those rankings is not fixed or announced in advance. In the past it has fallen between December 22 and 29 and lasted about a week.

What's certain is that the date is fast becoming the make-or-break moment for annual mobile gaming sales.

STRATEGIES

To clinch one of the 25 rankings on each of Apple's charts, the gaming industry has devised ever more technical tricks and marketing gimmicks, as the iOS market has evolved since the Apple's first iPad tablet was launched in 2010.

This year, game companies have become "more sophisticated" and "tactical" in the way they design and price content, following the early experimental years, beginning around 2010, said Nick Earl, senior vice president of Electronic Arts.

And game publishers have honed the ability to respond quickly to gamers and immediately tweak content and difficulty levels in real-time to push sales, Ellie Fields, senior director of product marketing at data visualization software company Tableau Software, said.

Strategies vary widely between companies. Some may focus on clever advertising while others craft holiday deals to generate a buzz around titles.

Smaller players like TinyCo and Pocket Gems may not have Electronic Arts' brand advantage so they cross-promote games and enter deals to advertise on their competitor's hit titles.

Say a mobile games maker invests $1 on a banner ad to acquire a new user and it learns through data analytics that the user is spending $2 in its game. Around Christmas, it can raise its ad budget in real-time or in advance and target a top-selling device, geographic location or demographic group, Alegre explained.

The ad strategies used to be a lot less smart but "right now people are more data driven and focused," Alegre said.

Electronic Arts' mobile label has planned 350 promotions, ranging from reduced rates to holiday-themed game content updates. The company uses data analytics and strives to maintain a daily deals site, tweaking rates and game offerings based on demand.

"We've really got smarter on what kind of deals to make available, when they should be unveiled, how many at a time and how many in parallel," Earl said.

The company's "Simpsons: Tapped Out" game based on the popular animated series was halted after its spring launch as its servers failed handle heavy traffic.

The city-building game was re-launched and this holiday has Homer Simpson's fictitious hometown of Springfield all snowy and adorned with Yuletide decorations.

For the Christmas period, technical stability is Electronic Arts' "No. 1 priority," Earl said.

DOWNLOAD VOLUME

The industry experiences a torrent of download activity starting on Christmas Eve until the first week of January as consumers use up app gift cards like iTunes gift cards.

In the last two years, the mobile gaming space has exploded as new tablets and phones flooded the market. Last Christmas about 7 million mobile devices were activated, compared to 2.8 million devices in Christmas 2010, according to mobile analytics firm Flurry. That's about seven times the number of Google Inc's Android devices activated on a normal day.

Android, which does not freeze its charts, has a lot more distribution but users spend less money than on Apple's iOS devices, analysts say.

Without providing details, EA said the number of its iOS games downloaded on Christmas day last year was 500 percent higher than the average daily download rate for all of 2011.

This presents a narrow, focused window for game companies like Electronic Arts and Disney Mobile to plug their games and landing them on app download charts maintained by hardware makers like Apple and Google.

That in turn spawned sophisticated strategies to handle the intense competition, Bart Decrem, Disney Mobile's senior vice-president, said.

Data analytics systems will be a revenue-driving weapon for mobile game companies on Christmas morning, Alegre said.

(Reporting by Malathi Nayak; Editing by Richard Chang)

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