English Bus/Financial Marketing

"Developing regions are not only growing faster, but exceeding expectations," said Loren Loverde, director of IDC's Worldwide Quarterly PC Tracker, in a statement. "Although this is an important development trend, it's also the case that the bulk of portable PC adoption " the leading market drier " remains concentrated in the more mature markets."

This sentence makes perfect sense to me if I omit "leading market drier."
Can anyone clue me in to what this means? Thanks in advance :-)