The snack market is booming, bringing in a whopping $605 billion in global sales last year, and there are even more growth opportunities ahead, according to Citi.

In an environment where consumer tastes are changing, the demand for snacks has only gone up, especially in the U.S. “The average number of snacks consumed per day in the U.S. more than doubled since the late 1970's from 1 to 2.5 today. Moreover, 40% of U.S. adults in the late ‘70's didn't snack at all on any given day! Now, 95% of U.S. adults consume at least one snack daily,” analyst David Driscoll wrote in a note Wednesday.

So, what snacks are people reaching for the most? Within snacks, the largest global category is chocolate, which brought in about $110 billion in sales and accounts for 18% of the market. Second was salty snacks, which brought in $83 billion and represents 14%. Ice cream ranks third with about $77 billion in global sales and 13% of the total snack market. Fourth was sweet biscuits, raking in about $73 billion and representing 12%. Rounding out the top five is sugar confection, or candy. That group brought in $63 billion in sales and accounted for 10% of the global snack market. “In aggregate, these top 5 snacking categories represent 67% of global snack sales, or $406B in annual sales.”

Snacks’ rise in popularity is due to social and economic shifts, Driscoll argued. It is no longer just a treat, but snacks now also serve as a primary source of fuel.

“The rise in snacking occasions in the U.S. over the past 40 years has been driven largely in part to social and economic shifts, including consumers having busier, faster-paced lives, more women in the workforce, and smaller households. Consumers now need or want to eat more on the go, or cooking full sit-down meals is not as much as priority,” Driscoll said.

Given the increase in snack consumption, Driscoll sees major opportunities for businesses. Not only is demand is strong, but margins are also better with snacks. “One benefit of selling snacks is that they generally offer manufacturers comparatively better margins relative to other categories,” Driscoll said. “When we break out snacks, when possible, from individual company disclosures, our analysis indicates operating margins at or above the 14.7% operating margin for food globally.”

In developed markets, snacks are growing faster than total food. “This a key reason why large global food companies are increasingly trying to shift their portfolios—and their narrative—toward snacks,” Driscoll explained.

North America and Western Europe are currently the largest snack markets, accounting for nearly 50%. According to Driscoll, the developed markets represent about 60% of total sales, while emerging markets represent the remaining 40%.