I am curious (and I know this is a site where someone will know such things): How likely is it for a bombing to remain unsolved in the United States? I read somewhere that there were multiple bombings per year in the US in the 1970s (usually with little or no loss of life); how many remained unsolved? I assume low profile casualty-less bombings may not attract a lot of resources, but what about bombings which resulted in deaths or injuries? How many remain unsolved?

I ask because I wrote on someone's facebook page (he is a psychiatrist who proposed, perhaps in jest, that this may have been the act of a disabled person who hates superfit marathoners) that "in any case, we will know soon"...then started thinking, will we?

What do the experts say?