The hot housing market is claiming another casualty: buyer’s agent commission.

Real estate agent’s commission rates have been on the decline nation-wide for several years, according to discount brokerage Redfin, which published the study of MLS home-sale records last week.

The average buyer’s agent commission rate in America was 2.75 percent in November 2017, and slid down a few basis points over the next few years amid seasonal fluctuations before diving off a cliff in the spring of 2020. The rate hit 2.69 percent in November 2020 and kept falling before hitting 2.63 percent in November 2021. In dollar terms, the average buyer’s agent commission was $12,415 in November of last year, up from $11,608 a year before and $9,610 in November 2017.

Redfin’s analysis singles out the immense power sellers have wielded in the real estate market over the last two years for blame.

“One might think the surge in home prices that’s driving up commissions in dollar terms is also what’s causing sellers to offer lower commission in percentage terms, but that’s likely not the case,” Redfin Chief Economist Daryl Fairweather said in a statement. “Instead, sellers are probably offering lower commission rates because they realize that a well-priced home in this extreme seller’s market will likely attract buyers on its own.”

The report also cites anecdotal evidence from Redfin agents who say that lower-priced homes see the lowest commission rates. In addition, the report says, additional features added to online listings in the last year, like 3-D tours, have helped buyers do a lot of their own research, or even find the home they want to buy. Nearly all buyers searched for a home online last year, the National Association of Realtors reported recently, and most did that research before reaching out to an agent.

Redfin’s brokerage model charges customers lower commissions than traditional brokerages, but pays its real estate agents a base salary, which traditional brokerages typically do not. The company has claimed in the past that it’s a more consumer-friendly model, but traditional agents have criticized the practice as unfairly undercutting its competition.

The lowest buyer agent commission rates of the 32 major metros Redfin studied (no Connecticut areas were included) were found in Nassau County, New York on Long Island. There, buyer’s agents were paid 1.98 percent of the home’s sale price for the three months ending Nov. 30, 2021, Redfin said, down from 2.02 percent in the same period the year before. That equated to $14,120 last year and $13,225 the year before. In the next-lowest metro, Greater Boston, buyer’s agents got paid an average of 2.21 percent of a home’s sale price, or $16,637 per sale, up from $15,336 a year before.

One reason for the low percentages, the study speculated, is that Massachusetts and New York State require attorneys preside over closings, potentially reducing perceptions of how much work a buyer’s agent does.

The highest buyer agent commission shares were paid out in Columbus, Ohio and Kansas City, Missouri (both 2.94 percent) in the fall 2021 window the study examined. The highest average buyer agent commission, in dollar terms, was found in St. Louis, Missouri ($41,505) and Oakland, California ($28,026).