There are five ways to increase anti-missiles rate:
1) Iron drome (existed)
2) Anti-missile missiles (suggested)
3) various form of anti-missile projects like it can upgraded like Iron drome, Patriach missile etc (suggested)
4) introduce technology to dedicate the percentage of anti-missile ability (suggested)
5) armys have tank to missile, aircraft to missiles, navy to missiles (suggested)
@Vincent:
and lastly, even you 100% knock out the missile,but its still take minimum causalities if the knock down area is close to a nation (imagine it is a reality), thus it may also giving minimum amount of damage...