MTBA vs SPMB

MTBABSimplify MBS ETF

SPMBAState Street SPDR Portfolio Mortgage Backed Bond ETF

In short

MTBA Most funds in the aggregate-bond aisle buy a little of everything. Simplify's mortgage ETF goes one lane deep: agency mortgage bonds, actively run, launched in 2023, paying monthly.

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

MTBA The fund seeks total return while preserving capital through prudent investment management.

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

• MTBA Costs 0.25% a year, below the 0.36% median for its bond-fund category. Cheap for an actively managed sleeve.
• One clear job: total return while preserving capital, per Simplify's own mandate. A specialist tool, not a repackaged broad-market index.simplify.us
• Pays monthly, has pulled in real assets since its 2023 launch, and trades with moderate volume for a niche bond fund.
• Lands in the upper half of a crowded aggregate-bond field, and its holdings line up closely with the mandate it advertises.

• 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

• MTBA The index heavyweights undercut it hard: BND, SPAB and SCHZ all run at 0.03%. You are paying up for active mortgage selection.
• This is one slice of the bond market, not a diversified core. No corporates, no Treasuries ballast beyond what the mortgage sleeve holds.
• Launched in November 2023, so its track record is short by bond-fund standards and spans only one rate environment.

• 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 MTBA profile⁠

Full SPMB profile⁠