The 6.8 per cent contraction in Japan's economic growth in the April-June quarter might not be just the first sign that the boom induced by the policies of Prime Minister Shinzo Abe is fading - but that it has been erased altogether in only three months. High Frequency Economics' chief economist Carl Weinberg calculates that Japan's potential gross domestic product is now back to the trend rate of decline it was in before Abenomics took hold. It's no coincidence, in Weinberg's view, that the fall in GDP follows directly from the March 31 ending of Japan's fiscal stimulus programme.