Japan raised its consumption tax to 8 percent from 5 percent in April. While a ramp-up in spending before the tax hike boosted the economy in the first quarter, economists have anticipated a slowdown in growth in the months ahead as the consumption tax bites.
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Still, the first-quarter GDP data may suggest that Japan's economy is in better shape than anticipated to whether the impact of the tax increase.
"So far, much of Abenomics has been dependent on money printing, on the action of the central bank and a weaker yen, but what we are seeing now is really strong consumer demand and business has been pulled forward as well," said Shulz.
"Everybody is counting on the central bank coming in this year again when the economy is slowing, but so far it looks strong and the second quarter will not see a big drop as the 6 percent we are seeing in terms of the jump right now," he added.
The blue-chip Nikkei stock index opened down 0.9 percent in early trade, while the yen firmed to its strongest level in almost a week, trading at about 101.70 per dollar.
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"The numbers are stellar (but) they are polluted due to the consumption tax increase, " said Paul Krake, founder of View from the Peak: Macro Strategies.
"There was a lot of front-loading that went into the data but the reality is, the number this big is actually bad news for asset prices going forward because it stalls policy momentum," he added.
The Bank of Japan has pumped cash into the economy over the past year to help weaken the yen, engineer a turnaround in the world's third biggest economy and end deflation.
Many analysts have been expecting further monetary stimulus to help the economy offset the impact of the consumption tax hike.