Speaking of the state of Earth at the start of the movie, one detail completely overlooked is an actual date for the events of the film. Most sci-fi love to proudly state when their version of the future is - Interstellar's touchstone, 2001: A Space Odyssey has it in the title - giving a very concrete view of the future. The obvious danger with this is that when we do get to that year (2015 is, finally, the year Marty McFly visited in Back To The Future: Part II) it all looks a little silly. Nolan probably understands the longevity of his film and kept things vague on purpose, but that doesn't stop it being a niggling question in need of solving. We know that the blight hasn't been around for generations - Donald, Cooper's father, talks about humanity in a time before things went tits up from first-hand experience, while Murph's teacher directly talks about the excess of the 20th Century, meaning our actions now lead directly into the general events of the film. Potential Answer: Using the actor's ages for reference, Donald is probably in his late-sixties and Cooper in his early-forties. As the former has strong memories of the present and the barrage of new gadgets, we can assume he was born in the 1990s or 2000s, putting the latter's birth sometime in the 2020s. This implies the blight is in our near future and the film probably starts in the 2050s or 2060s, running through to the next century.
