Asteroids

Is it worth to spend millions defending our planet?

Experts once believed that asteroids collide on Earth once a century, but new research has shown that an asteroid explodes in our atmosphere every decade or two, so I think that it is necessary to defend our planet.
But, is it worth to spend millions to defend our planet? I think we should search a way to know exactly when and where asteroids would collide. Because nowadays we dont know when it would collide and if it happens, it will be too late to do something against it. There's not doubt that if an asteroid explodes in a country or a city, the destruction will be bigger than anything we have seen an all time.
So I think that it is necessary to spend money defending our planet because if it occures, people won't notice on time and many will die.