Rutherford centralized organizational control of the Watch Tower Society. In 1919, he instituted the appointment of a director in each congregation, and a year later all members were instructed to report their weekly preaching activity to the Brooklyn headquarters. At an international convention held at Cedar Point, Ohio, in September 1922, a new emphasis was made on house-to-house preaching. Significant changes in doctrine and administration were regularly introduced during Rutherford's twenty-five years as president, including the 1920 announcement that the Jewish patriarchs (such as Abraham and Isaac) would be resurrected in 1925, marking the beginning of Christ's thousand-year Kingdom. Disappointed by the changes, tens of thousands of defections occurred during the first half of Rutherford's tenure, leading to the formation of several Bible Student organizations independent of the Watch Tower Society, most of which still exist. By mid-1919, as many as one in seven of Russell-era Bible Students had ceased their association with the Society, and as many as two-thirds by the end of the 1920s.