An average witness in Germany takes roughly 100 years to convert ONE person. (27 million hours for 2600 baptisms, ca. 9 hours/month)
But if 40 % of these are through informal witnessing, so that only 1236 of the 2600 baptisms are through the regular work, it would be be 166 years for an average publisher to convert one person in the regular ministry.
Given that 90 % of the baptized persons are children of witnesses (so that only 10 % are outsiders and 60 % of these 10 % were gathered in the door-to-door work), it would be 1660 years to convert ONE person through the door-to-door ministry.