President Xi Jinping's relentless campaign against official corruption will soon enter its fourth year without any sign of abating. True to his vow, it has taken down scores of "tigers" as well as "flies" - powerful officials as well as less senior bureaucrats. It seems hardly a day passes without news of an official being investigated for serious violations. No one appears to be above the law, as shown by the downfall of a former member of the Politburo Standing Committee, a former top aide to Xi's predecessor Hu Jintao and two former deputy chairmen of the Central Military Commission. And no one is beyond it either, with investigators having been sent to the provinces as the purge of corrupt central government officials continued.

In every province, they have arrested officials with the rank of deputy governor or above, most still in office. But this did not include city officials of Beijing and Shanghai, the latter being the power base of former president Jiang Zemin . Speculation has grown about who might be taken down in these two most sensitive centres.

News last week of investigations of Shanghai vice-mayor Ai Baojun and deputy Beijing party chief Lu Xiwen is therefore a landmark in the campaign. It will prompt observers to wonder whether it could be followed by an easing of the crackdown. After all, the bureaucracy has been complaining for some time that the campaign, and Xi's very public brake on official extravagance, has resulted in officials avoiding decisions they fear could get them into trouble. Business in turn is complaining about bureaucracy dragging its feet on important policy issues as the economy slows, with the latest inflation figures showing deflation is deepening.