Goldman Sachs holds the top spot among U.S. fixed-income dealers, according to a report from Greenwich Associates released Tuesday. Goldman had 12.1% of all market share based on institutional trading volume over the past 12 months, followed by Deutsche Bank (11.7%) and Citi (11.5%), according to Greenwich's data. J.P. Morgan and Barclays round out the top five with 11.4% and 10.3%, respectively.

Low rates and lack of volatility have dug into dealers' revenues, while new regulations have increased the cost of business.

Against this backdrop, Greenwich says those weathering the storm the best are banks with the largest platforms and smaller niche dealers, as midsize dealers feel they “are getting squeezed.”

Five of the six largest bulge-bracket U.S. fixed-income dealers increased market share. They account for 57% of the total market today vs. 53% a year ago.

Data were collected between February and April 2014.