The primary conclusion from the analysts' report is that "monetary policy may have added to inequality to the extent that it has boosted equity prices."
"Since 2010, high equity returns have been the main driver of faster growth of net wealth at the top of the distribution," they wrote.
Central bank asset purchases designed to push investors further out the risk spectrum have fostered a decline in the equity risk premium, which is positive for stocks.
Increases in home prices tend to serve as a moderating force on wealth inequality, as poorer households have a higher portion of their assets in real estate than the rich.
But no central bank has a mandate to target wealth inequality; indeed, while monetary policy may be exacerbating inequality, it's an ill-fitting tool to directly reduce it.
"The main contribution that the Fed can make to inequality, given that we don't have policies that target particular groups in the labor force, the main contribution we can make is to make sure that the labor market is performing well, that we attain Congress' maximum employment objective," Federal Reserve Chair Janet Yellen said during her semi-annual testimony before Congress.
Trends in financial markets, however, undoubtedly factor into monetary policymakers' decision-making process. For instance, the Federal Reserve indicated that financial market turmoil was a reason to refrain from raising rates in September.
But declines in stock prices disproportionately hurt the wealthiest individuals—ones who have a lower propensity to consume any extra dollar they receive.
If anything, the BIS' analysis may imply that if monetary policymakers want to help reduce wealth inequality, they ought to actively lean against the notion of a 'central bank put'—or the idea that a decline in equity prices to a certain level would inevitably trigger an accommodative response.