State Street’s (NYSE: STT) State Street Global Advisors (SSgA) unit, the third-largest U.S. issuer of exchange traded funds, delivered some good news for investors in popular sector ETFs, such as the Energy Select Sector SPDR (NYSEArca: XLE) and the Health Care Select Sector SPDR (NYSEArca: XLV): Another quiet fee reduction.

In a prospectus filed with the Securities and Exchange Commission at the end of January, SSgA revealed it has lowered the annual expense ratios on the nine sector SPDR ETFs, the largest group of sector ETFs to 0.15% from 0.16%.

SSgA’s new fee reductions on the nine SPDRs come a year after the company lowered expenses on the nine ETFs to 0.16% from 0.18% per year. Other well-known members of the sector SPDR suite include theFinancial Select Sector SPDR (NYSEArca: XLF), Technology Select Sector SPDR (NYSEArca: XLK) and the Industrial Select Sector SPDR (NYSEArca: XLI). [A Quiet Fee Cut From SSgA]

Earlier this week, SSgA said it trimmed fees on 41 of its other ETFs across multiple asset classes, including fixed income, emerging markets and low volatility funds. That announcement featured some notable expense ratio reductions with several of the ETFs seeing their fees cut by 50% or more. Ten other ETFs affected by that announcement now have annual fees of 0.4%, down from 0.5%. [SSgA Pares Fees on 41 ETFs]

Sector ETFs are increasingly popular with advisors and investors, but with that growth has come intense competition. At the end of last year, there was over $310 billion allocated to sector ETFs. Over the trailing 12 months, ETFs for 11 sectors (when breaking real estate out as its own sector) have gained assets, according to State Street data.

In December, Vanguard lowered fees on its 10 sector ETFs to 0.12%, putting the issuer into a tie with Fidelity for the least expensive sector ETFs. Fidelity, which entered the sector ETF fray with 10 funds that launched in October 2013, now has over $2.2 billion across those ETFs.