Fiksu said that availability of the iPhone 4S in October 2011 caused a “large spike in mobile app downloads,” following several months of declines.

According to the company’s App Store Competitive Index, there was “as much as a 70 percent increase” in download volumes during the iPhone 4S launch weekend, and a 40 percent increase post-launch, when compared to the period before availability. It was noted that while the figures usually capture mostly new app downloads, following the launch of a new device this also includes customers re-downloading products to their new handsets.

The company said that there were 4.91 million downloads in October, compared with 3.8 million in September. Factoring in the number of apps being re-installed by the same users, the company believes the “likely net volume” was 4.5 million new downloads.

Fiksu said that during the peak weekend, mobile marketing costs remained high, then fell in the weeks that followed due to decreased costs in traffic. By the end of the month, its Cost per Loyal User Index netted out to US$1.47 – compared to September’s “all-time high” of US$1.64.

Micah Adler, CEO of Fiksu, said: “For mobile marketers seeking a window of extreme growth regardless of cost, the iPhone 4S launch presented a bonanza to secure large volumes of new users. But for those seeking to maximise value and ROI, the best bet was to resist the temptation to join the initial rush. Our advice to cost conscious marketers was to wait it out for a week and then take advantage of the efficiencies in heightened volumes at significantly lower costs."