My latest report – on wireless usage and advertising trends in the BRIC countries (Brazil / Russia / India / China) – launches today. Given their large populations, some of the numbers are understandably eye-popping. The full report is available here for Total Access subscribers, but here are a few stats that stand out:

• Over 200 million mobile subscribers in both Brazil and Russia by 2014
• 853 million subscribers in India by 2014
• 1.3 billion (yes billion) subscribers and 957 million mobile Internet users in China by 2014

The China stats highlight a key trend I identify in the report, namely that mobile subscriber growth is slowing, but mobile Internet user growth is speeding up. The days of triple-digit subscriber growth are long past. And as subscriber bases solidify, it is now the mobile Internet user populations that are increasing rapidly, albeit from small bases.

They also reveal the degree to which the adage “Everything is bigger in Texas” applies equally to China. Staggering as it may to conceptualize, there will be more mobile Internet users in China in 2010 than the entire population of the US.

Granted, these mobile Internet users do not currently monetize as well as smaller mobile audiences in, say, the US, so aggregate mobile advertising spending levels in China are still low relative to the size of the mobile Internet user base. Nevertheless, the growth trend is significant, and China’s mobile subscribers and Internet users will generate by far the highest advertising spending among the BRIC nations ($223.2 million in 2010, more than tripling to $699.9 million in 2012).

It’s easy to get caught up in the lure of big numbers and overlook the reality on the ground. The fact is that even as a rising number of consumers are purchasing smartphones, many mobile users across the BRIC footprint will remain on less sophisticated devices and legacy second-generation mobile networks well into the middle of the decade.

For marketers interested in reaching the bulk of BRIC mobile consumers today, this means emphasizing messaging campaigns and reserving flashier mobile sites and applications for the small vanguard of smartphone users. By the same token, marketers should also be prepared for changing behaviors as network speeds increase and mobile consumers graduate to more expensive devices and data services.