Destinations routinely measure visitor arrivals, total expenditure and year-on-year growth. Those measures describe how demand has changed. They reveal much less about what that demand depends on.
Two destinations can grow at the same rate while becoming structurally very different. One may be building a balanced visitor portfolio. The other may be becoming more dependent on a narrow source of demand.
That distinction is the starting point for this diagnostic.
Portfolio structure tells you what that growth depends on.