A couple of references I found...
*** yb75 p. 124 United States of America (Part Two) ***
TO THE FIELD!
The Watch Tower
of August 1 and 15, 1919, carried the two-part article "Blessed Are the Fearless." Plainly it showed the need for faithful and fearless action in God’s service. The response to this call to fearless action on the part of Jehovah’s people was enthusiastic and courageous. They zealously undertook the Kingdom publicity work that was now set before them. They became spiritually alive again in Jehovah’s active service as his ambassadors. Thus was fulfilled the prophetic picture of the resurrection of God’s "two witnesses" as described in Revelation 11:11, 12.
In 1920 personal responsibility for preaching was more keenly felt as participants in the witness work turned in a weekly report of activity. Prior to 1918 only colporteurs made field service reports. Also, to facilitate the preaching activity, congregations were given specific territory assignments. What were the effects? In 1920 there were 8,052 "class workers" and 350 colporteurs. By 1922, of more than 1,200 congregations in the United States, 980 had been fully reorganized to engage in the field service. These had 8,801 workers who placed Bible literature with householders on a contribution. The weekly average was 2,250.
*** w55 5/15 p. 299 Part 10: Modern Restoration of True Worship (1919-1932) ***
A tightening up of preaching responsibility began in 1920 by requiring every one in the congregation who participated in the witness work to turn in a weekly report. Prior to 1918 only the pioneers were required to report their service activities. Definite territory assignments were now being made to the congregations for their field activity. Truly the congregations were being "yoked" for service. For the first year of such reporting, 1920, there were 8,052 "class workers" and 350 pioneers. Of the more than 1,200 affiliated congregations 980 were reported by 1922 as being fully reorganized to engage in the field service with 8,270 "class workers." Beginning in 1923 several Sundays were set aside for "world-wide witness," to encourage united efforts all over the world in holding simultaneous public meetings using the subject "Millions Now Living Will Never Die" and also for united participation in advertising the lectures.