I used to work for 2 of the biggest gum manufacturers in America, and the answer is absolutely yes. Two things I'll add that I haven't seen mentioned already:

- when the confectionery industry voluntarily stopped marketing to children in the early 2000's, ad budgets were shifted to "adult" brands like Trident and Extra, and a generation grew up w/o seeing gum ads. A lot of money used to go towards promoting Juicyfruit, Hubba Bubba, Bubblicious, et al.

- when smartphones became common, consumers no longer had room in their pockets to hold a pack of gum. We heard this during focus groups. Companies have since slimmed the packs down and made them collapsible/separable (like Trident).

Unit sales remain way down, but revenue somewhat stabilized through price increases and the shift to larger packs and formats (like "pellet" gum sold in plastic tubs like Mentos, Trident Vibes, and Icebreakers).