CREATE TABLE table_66703 ("Year" CLOB, "Births  ( 000s ) " FLOAT, "Deaths" FLOAT, "Natural Growth" FLOAT, "Total Fertility Rate" CLOB)

What is the average birth rate that has a total fertility rate of na, and a natural growth smaller than 2.5?
SELECT AVG("Births (000s)") FROM table_66703 WHERE "Total Fertility Rate" = 'na' AND "Natural Growth" < '2.5'
SELECT AVG("Births (000s)") FROM "table_66703" WHERE "Natural Growth" < '2.5' AND "Total Fertility Rate" = 'na'