SINGAPORE (Reuters) - For the first time in more than three decades Japan's economy, the world's second largest, is set to be surpassed in size by the rest of Asia.

That milestone, says Lehman Brothers economist Robert Subbaraman, signals the arrival of the Asian consumer as a key growth driver and probably marks the turning point for Asia's export-led economic model.

While only a small number of Asia's more than 3 billion people are moving up to middle-class income levels, analysts say the numbers are growing faster than any other region worldwide, fuelling a consumption boom.