On Wednesday, Apple (AAPL -0.81%) will report what some analysts consider its most important earnings release in a decade. This particular report is crucial not only because of lofty expectations surrounding the new iPhone 5 and iPad Mini, but also because investors have gotten their confidence beaten out of them because of the monstrous 30% pullback since September.

Here's one more thing to listen for on Apple's earnings conference call: China.

Can you hear me now?
Much ink has been spilled over Apple's incredible growth prospects in China, but only recently has the company begun providing real detail into its financial performance in the Middle Kingdom. Apple defines its Greater China segment as Mainland China, Hong Kong, and Taiwan.

The reason investors have to listen for it is because CEO Tim Cook now provides that information on the conference call, typically when asked directly by an analyst. This hasn't always been the case, but Cook has taken to giving out these figures recently. For example, the only reason investors know that Greater China revenue was approximately $858 million in fiscal 2009 was because Cook said that geographical segment comprised 2% of sales that year -- a revelation he didn't reveal until the Q4 2011 conference call.

This data isn't contained in any of Apple's press releases or SEC filings, but it's one of the most important areas for investors to keep an eye on. That's especially true since Cook recently said he expects China to eventually surpass the U.S. as Apple's biggest market. The company still has its work cut out for it, since the U.S. and China generated respective revenues of $61.3 billion and $23.8 billion in fiscal 2012.

Source: Apple conference calls.

For context, in the previous fiscal first quarter release, Greater China generated revenue of $4.5 billion. There are also a couple factors to remember when judging Apple's seasonal performance in China. While the December quarter is the big holiday shopping season in the U.S., the March quarter includes Chinese New Year over there.

It's all about timing
In fiscal 2012, sales jumped 75% sequentially to $7.9 billion heading into the March quarter. On top of that, the iPhone 5 didn't officially launch in Mainland China until December, where the device garnered 2 million sales during the first weekend. The curveball is that Hong Kong was among the launch countries in September, and there is a very active and very large gray market for smuggling iPhones into Mainland China, since ambitious smugglers were fetching upwards of $1,100 per unit when the iPhone 5 launched.

The same thing is true for the iPad Mini, which officially launched in Mainland China at the same time as the iPhone 5 in December, with the cellular-equipped models landing just this month. The iPad Mini saw strong demand at its official launch, with one analyst characterizing interest as "insatiable," since inventories were sold out at all of Apple's retail stores in China. The smaller tablet was launched in Hong Kong in November as part of the first batch of countries to get the device.

That means some initial demand for both of those devices could have been satisfied before the official launch for customers willing to pay a premium. Other prospective buyers may have had to wait until the New Year, after the fiscal quarter closed, to get their hands on iDevices.

Keep an ear out
Apple's geographical reporting standards could be improved for the sake of transparency. The company currently reports direct sales to geographical segments, but also a separate category for its retail operations. Since it operates retail stores in 13 countries, the company's retail results include numerous geographies and makes it harder for investors to isolate performance in specific countries.

Until then, investors will just have to keep an ear out on the conference call.