In their 2014 study, Drs. Martin Gilens and Ben Page tracked almost 2000 policy cases from 1981 to 2000, noting which policies were enacted and which were not. These policy decisions were matched to survey data of U.S. citizens, looking at socio-economic groups and whether or not each group favored the policy according to polling (read the article here).
The short story: the more the economic elite favor a particular public policy, the higher the probability that it will be enacted.
Their study echoes an earlier study by Dr. Larry Bartels showing a similar, though less pronounced, responsiveness of the Senate to constituent desires based on income classification.