8973, Zamboanga del Sur's representation was reduced to two districts. The former third district first elected a representative under the designation Lone congressional district of Zamboanga Sibugay beginning in the 2001 election.
In Zamboanga del Sur, the third district was divided into two districts.  The former third district's representative began serving as a lone representative for Zamboanga Sibugay starting in the 2001 elections.