Did you folks have a Home Inspection??? If so, what did he/she say about it?
The cause of the bow is not going to be easy to determine. You said that the home is a 'new home' but I don't think you mean you bought a home that was just built, no/yes?
If the plaster is from the original 1930's (meaning that the home is not a 'new home' per my definition), the cause could simply be a build-up of plaster. As to why that is, I can't say. It could be that something is 'pushing' the wall out. It could be the 'character' of the home.
From the limited information you've provided, you may need a Pro to take a look at the situation. W/O knowing the cause, it's hard to answer your questions on how to fix it, on whether or not the wall needs to be 'replaced', or what to do to minimize the problem.
NOW, if the wall is simply drywall, maybe it needs more screws. Or maybe the insulation has 'fallen' and over the years has pushed the wall out. Again, someone needs to evaluate the situation before a solution can be offered. And that is something none of 'us' can do from here. ONCE you find out the cause, come back and we'll 'talk' about a solution.
My best to ya and hope this helps.
Jay J -Moderator