Just over a month after being released, Apple's (NASDAQ:AAPL) iPhone 5s and 5c account for 5.5% of worldwide iPhone activations, according to data from Localytics.

To fully understand that figure, let's take a look at how the new devices stack up against total iPhone 5 activations and see how this matches last year's iPhone usage statistics.

During a four-week time period this year, Localytics looked at 40 million unique iPhone activations worldwide and found that the iPhone 5 is still the most popular Apple smartphone, with 40% of activations.

The pie chart below shows the breakdown of iPhone activations:

Iphone Activations
Source: Localytics.

The 4s still has an amazing 32.9% share, which may not be all that surprising considering Apple chose to continue selling the 4s while dropping the 5 from its lineup.

It's important to give some perspective to the current activation numbers by comparing them to last year's iPhone 5 data. According to Localytics back in December 2012, the iPhone 5 accounted for 12% of iPhone devices.

Iphone Activations
Source: Localytics.

Of course, there's at least a month's worth of data discrepancy between this year's iPhone 5s and 5c activations and iPhone 5 usage last year. This means the next month could be an important time for investors to monitor. Considering that the holiday shopping season is nearly here, it's possible the new devices could make up the gap between now and the beginning of December.

What will be interesting to watch is how well the 4s continues to hold up against the 5s and the 5c. The device is now free with most two-year activations, and runs iOS 7. Though it clearly doesn't have the same features, screen size, or speed as the newer devices, it may still prove to be a popular choice for consumers. Apple only offers the 4s in the 8 GB option, which is good for Apple investors considering that the company likely has low manufacturing and inventory costs for the 4s because the device is older and doesn't have multiple hard drive configurations.

Over the next few months, investors should continue to track how the new iPhones are doing compared to iPhone 5 activations. The iPhone 4s shouldn't hurt sales of the 5s or 5c, as the two are in different price brackets than the older device and have significantly more features. With the holiday season almost here and the iPhone 4s being offered for free with a two-year contract, Apple has set itself up for a solid current quarter.

Fool contributor Chris Neiger has no position in any stocks mentioned. The Motley Fool recommends Apple. The Motley Fool owns shares of Apple. 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.