CREATE TABLE table_51566 ("Year" FLOAT, "Award" TEXT, "Category" TEXT, "Nomination" TEXT, "Result" TEXT)

What was the total number of years than had best improved singer ( )?
SELECT SUM("Year") FROM table_51566 WHERE "Category" = 'best improved singer (躍進歌手)'
SELECT SUM("Year") FROM "table_51566" WHERE "Category" = 'best improved singer (躍進歌手)'