Group by continent. Organizing a flat list of 50 items into 7 groups of 7[1] should improve accessibility, if the categories make any sort of sense. I would be

Group by continent. Organizing a flat list of 50 items into 7 groups of 7[1] should improve accessibility, if the categories make any sort of sense. I would be interested in seeing research comparisons of flat dropdown vs grouped dropdown (ie some items are unindented unselectable categories) vs double-dropdown, where the items available in the second are determined by the selection of the first. [1] For the purposes of dropdown menu length, 49 is equal to 50.