CMBS vs SPMB

CMBSCiShares CMBS ETF

SPMBAState Street SPDR Portfolio Mortgage Backed Bond ETF

In short

CMBS The index route into commercial mortgage bonds: debt on offices, hotels, malls and apartment blocks rather than home loans. Running since 2012, screened to investment-grade, top-of-the-waterfall slices.

SPMB The no-frills way to own America's mortgage bonds. SPMB tracks the Bloomberg U.S. MBS Index for four basis points, a fraction of what the typical mortgage-bond ETF charges, and pays income monthly.

Stated mandate

CMBS The fund seeks to track an index composed of U.S. investment-grade commercial mortgage-backed securities.

SPMB The fund seeks to track, before fees and expenses, the price and yield performance of the Bloomberg U.S. MBS Index.

Why people hold it

• CMBS The index takes only ERISA-eligible tranches with first priority of principal repayment, rated in one of the three highest categories, plus minimum deal and tranche sizes.sec.gov
• 0.25% a year sits under the 0.30% median fee for mortgage-bond ETFs, notable for a corner of the market this specialized.
• Roughly 500 bond positions, monthly distributions, and a track record going back to its 2012 launch.
• Single mandate, clearly stated: track an index of U.S. investment-grade commercial mortgage-backed securities. No credit tourism, no off-benchmark detours.ishares.com

• SPMB Four basis points a year, against a 0.35% median for mortgage-bond ETFs. Cost is where this fund does its loudest talking.
• Runs the same Bloomberg U.S. MBS Index as iShares' MBB at the same 0.04% fee, and undercuts MBBA, which tracks that index for far more.
• Roughly 2,700 mortgage bonds in a single line item, inside a multi-billion-dollar fund that trades actively, with distributions paid monthly.
• Trading since 2009, and one of the strongest implementations in its mortgage-bond peer group.

Worth knowing

• CMBS Thinly traded next to the agency-MBS giants in its category, so the spread you pay and the order type you use matter more here.
• Cheap for a niche, still not cheap outright: agency-mortgage peers VMBS and SMBS run 0.03%, so broad mortgage exposure costs a fraction of this.
• BlackRock flags prepayment and extension risk on these bonds, and notes small interest-rate moves can sharply cut the value of certain mortgage securities.ishares.com

• SPMB Homeowners refinance when rates fall, so mortgage bonds get paid back early and rally less than Treasuries. That quirk is built into the index, not the fund.
• Prices move with interest rates and the monthly payout floats with the portfolio. This is a bond fund, not a cash substitute.
• US mortgages only. No Treasuries, no corporates, no credit spice. A building block for a bond sleeve rather than the whole sleeve.

Full CMBS profile⁠

Full SPMB profile⁠