Short answer - consumption. Gotta say I would not be surprised if consumption gives GDP a bigger-than-expected boost, I'd be shocked!

Still, here is the reasoning I've heard from a few (in a nutshell):

Japan's Cabinet Office Synthetic Consumption Index

  • Attempts to synthesize consumption trends from demand-side statistics (Family Income and Expenditure Survey, etc.)
  • It has shown a close fit with national accounts measure of private expenditure

In Q1 as a whole it rose at its fastest pace in 3 years (on the other hand is did slow in March), at 0.9% q/q

  • which should contribute 0.5% to the GDP data

What to expect from Japan GDP? I posted on that here earlier, but to save you a click:

Japan kicks it off at 2350GMT with the first Q1 GDP estimate

  • GDP (seasonally adjusted) for Q1, preliminary, q/q: expected 0.5%, prior 0.3%
  • GDP Annualized (seasonally adjusted) for Q1, preliminary y/y: expected 1.7%, prior 1.2%
  • GDP Nominal (seasonally adjusted), preliminary q/q: expected 0.1%, prior 0.4%
  • GDP Deflator y/y, preliminary: expected -0.7%, prior -0.1%. The deflator is an inflation indicator. Ugh. Moving right along ....
  • GDP Consumer Spending preliminary q/q, expected is 0.5%, prior was 0.0%
  • GDP Business Spending preliminary q/q: expected -0.4%, prior was 2.0%