CREATE TABLE table_59540 ("Rank" FLOAT, "Local government area" TEXT, "Population 2006 census" FLOAT, "Population 2007 estimate" FLOAT, "Growth rate" TEXT, "Stat. division/district" TEXT)

What was the 2006 population for the local government area of alexandrina council whose rank was smaller than 19?
SELECT AVG("Population 2006 census") FROM table_59540 WHERE "Local government area" = 'alexandrina council' AND "Rank" < '19'
SELECT AVG("Population 2006 census") FROM "table_59540" WHERE "Local government area" = 'alexandrina council' AND "Rank" < '19'