Why does this plpgslq always return 1?

Can anyone tell me why this always return 1? Thanks!

CREATE FUNCTION passrate(date, date, text) RETURNS float AS '

DECLARE
begindate ALIAS FOR $1;
enddate ALIAS FOR $2;
passfail ALIAS FOR $3;
ret float;
countp float;
counttotal float;

BEGIN

SELECT INTO countp COUNT(*)
FROM benchmark
WHERE passfail = passfail;

SELECT INTO counttotal COUNT(*)
FROM benchmark;

ret := countp / counttotal;
RETURN ret;
END;'
LANGUAGE 'plpgsql';

John