It's not actually one of the Nobel prizes as set up by Alfred Nobel. The full name is the "The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel".
It was set up by the Swedish central bank to free ride on the good reputation of the actual prizes. Their motivation was to push economic policies beneficial to themselves (mainly promoting the political independence of central banks in the beginning).
The bank paid to establish it, but it is run by the Nobel Foundation, and the winners are selected by the Royal Swedish Academy of Sciences (which also selects the winners for chemistry and physics), and it follows the same rules as the original prizes.
I don't think anyone is looking at the Nobel prizes to categorise sciences.
The 'table of hard science' according to Alfred Nobel also includes medicine (not science, but we'll let it pass), literature (really not science), and peace (really really not science).
Anyway, the Nobel Prize for economics is not actually a Nobel prize anyway.
Some of it is hard science, with peer-reviewed papers, experiments and statistics. There is even some overlap with chemistry.
Some of it is engineering. Doctors are closer to engineers than they are to scientists. They have a problem (a sick patient who needs help), constraints (time, availability, cost, ...), tools (drugs, diagnosis tools, ...), and need to turn all that into a solution.
Some of it is craftsmanship. Surgeons are like mechanics for the human body, a job requiring dexterity and practical thinking.
Some of it is care. With nurses needing as much empathy as they need practical skills.
I agree that economics is more relevant to the average person than astrophysics, but I don't see what that has to do with its being a hard science. Physics has testable hypotheses and experimental verification. The attempts at this in economics put it at the absolute low end of the soft sciences, as far as I can tell.
> I don't see what that has to do with its being a hard science
I agree. I meant to make two separate claims.
> The attempts at this in economics put it at the absolute low end of the soft sciences, as far as I can tell.
Economics has many subfields. The major division is between microeconomics and macroeconomics.
I think a lot of the "soft science" reputation the field has comes from the Macro side. This is a very tough field to study, since the study object (the world economy) is sentient, extremely intelligent, and adapts to any new findings. It can certainly be seen as a partially failed science as a result.
Macro gets the headlines, but the Micro side is what I'm impressed by. We have an enormous amount of knowledge accumulated over the last 200 years, and understand society and markets immensely more than before Adam Smith started thinking about this stuff.
That's a pretty good point considering Turing award winners (computer science) get so little media exposure compared to Nobel winners. Same for Field medal winners...