The best sunscreens for 2018 have been named in Consumer Reports' annual list.

The group assessed 73 sunscreen lotions, sprays, and sticks labeled SPF 30 or higher, CBS News reported.

SPF (sun protection factor) is meant to indicate how well a sunscreen protects against ultraviolet B (UVB) radiation, which can trigger skin cancer.

"Every sunscreen is tested at the lab in the same way -- and we use sunscreens we buy off the shelves, the way a consumer would," Trisha Calvo, deputy editor of health and food at Consumer Reports, told CBS News.

The group said this year's top four sunscreens are: La Roche-Posay Anthelios 60 Melt-In Sunscreen Milk; Equate (Walmart) Sport Lotion SPF 50; BullFrog Land Sport Quik Gel SPF 50; Coppertone WaterBabies SPF 50 Lotion.

Of the 73 sunscreens tested, 24 had less than half their labeled SPF number, which means consumers may not be getting the amount of sun protection they expect, CBS News reported.

During its years of testing sunscreens, Consumer Reports has found that "natural" or "mineral" products with only titanium dioxide, zinc oxide or both as active ingredients have tended to be less effective than those with chemical active ingredients, such as avobenzone, the researchers said.

No mineral sunscreens made this year's list of recommended sunscreens, CBS News reported.