Markets everywhere

http://www.bbc.co.uk/news/11559801 reports that Fifa is investigating allegations that two of its officials offered to sell their votes in the contest to host the 2018 World Cup.  The key assumption in Economics is of course that people respond to incentives.  Do other social sciences have this at their core? I'm not sure.  One might say of course that most of the officials at FIFA are not selling their votes: but if enough do, that would be enough to determine the outcome of the competition.  Second key economic insight: everything is determined at the margin.