This story first ran in Financial Advisor IQ's sister publication, Ignites.

Mutual fund and ETF investors reaped average returns during the past 10 years that were 1.7 percentage points less than the total returns garnered by those products over the same period, according to Morningstar’s latest Mind the Gap report.

The 9.3% average 10-year return on each dollar invested lagged the 11% total return for the period ended Dec. 31 by roughly the same margin as the last four years’ shortfalls, which ranged from 1.6 to 1.8 percentage points, according to Morningstar.

The fund types with the most assets, U.S. equity and taxable bond funds, showed smaller gaps, with investors in both earning roughly 1.2 fewer percentage points, on average, than the total return.

The group of investors who experienced the smallest gap between their average earnings and the total return held allocation funds. The gap for those funds between investors' average returns and total returns was 77 basis points.

Investors in sector equity funds lagged the total return figure the most, falling nearly 4 percentage points behind, on average.

Poorly timed purchases and sales of fund shares cost mutual fund and ETF investors a sixth of the total return that they could have earned if they had bought and held those shares over the 10-year period, according to the report.

“To shrink the gap and improve results … investors should focus on holding a small number of widely diversified funds, avoid narrow or highly volatile funds, automate routine tasks like rebalancing, and embrace techniques that put investment decisions on autopilot such as dollar-cost averaging,” wrote a Morningstar spokesperson in an email.