What are the themes in the story "The Lottery" by Shirley Jackson?

Without question, tradition is a huge theme within "The Lottery," as the very existence of tradition is expressed in such a brutal way. It would be hard to read the story and not wonder about the ridiculous notion of carrying on a tradition where, for no reason, someone has to die, yet there the community is, carrying on the tradition, regardless.
Another theme at work though has to do with selfish interest since the vast majority of the outspoken cries against the lottery are only provided once the family has been chosen. Since the chosen understandably don't want to die, the time for speaking out has arrived, but it's drenched in that selfish interest. Their outcries against the lottery would have felt more solid and unbiased if they would've come before the event happened, which could be a reason why so little happens in consequence to those outcries. From there then, we're stepping into a theme of timing as well. 
Yet another theme would be the prettying up of matters that are unpleasant, perhaps society's tendency to do so. The community holds the lottery in a very organized way, and it has this ironic name that has a connotation of winning and gain. These details are things that make the situation feel less barbaric, though there can be no doubt that the circumstance is, in fact, barbaric.

A couple of major themes of this story have to do with the subject of tradition. First, the story conveys that people do not like to go against tradition, even if they do not particularly care for the tradition itself. The narrator says that when Mr. Summers spoke to the town about making a new black box for use during the lottery, people responded poorly because "no one liked to upset even as much tradition as was represented by the black box." Despite the fact that it's literally just a painted wooden box, and a box that has splintered and cracked and faded over the years, people are resistant to replacing it because it's the only box they really remember ever using. This notion seems pretty ridiculous: they are so stuck in their ways that they cannot see the value in replacing a "shabby" wooden box.
Second, the story conveys the theme that traditions should continually be evaluated for their cultural relevance and humanity. Clearly, this tradition of choosing one person to stone every month is inhumane and does nothing to better the community. There's talk, we learn, of another town over discontinuing their lottery, and so we know that such a reevaluation can take place. We surmise by the cruel way Tessie Hutchinson is stoned to death by her friends and family that such a reevaluation would be positive and right.