Comments by the Faithful & Discreet Slave class about those serving where the need is greater, specifically  in their relationship to the progress of the worldwide Kingdom Preaching work:

"What accounts for such progress? Many things. Missionaries trained at the Watchtower Bible School of Gilead and, more recently, upwards of 20,000 graduates of the Ministerial Training School have made a huge contribution. So have the many Witnesses who at their own expense have moved to lands where the need for Kingdom publishers is greater. Such self-sacrificing Christians—men and women, young and old, single and married—play a significant role in preaching the Kingdom message throughout the earth.  They are greatly appreciated."

Watchtower July 1, 2005, Pages 22-23

Comments by the Ecuador Branch office regarding those from abroad  who serve
where the need is greater in Ecuador:  

"These dear Witnesses take the lead in preaching in isolated areas, help to form new congregations, and  contribute   to the spiritual growth of the local brothers and sisters."

Watchtower July 1, 2005, Pages 22-23