We went with the first option. The base table for this approach is '''hcllayer'''. The variables are '''highest1hulllayer''', highest2hulllayer, and highest3hulllayer in the '''highesthulllayer''' table.
It is worth noting that the highest1hulllayer occurs on average at around 2135.49% unclustered (with std dev. of 2048.20%), but this falls to just 12.8% when we exclude years where the highest1hulllayer is also the last and hence only layer. These percentages go down alightly slightly for highest2hulllayer and highest3hulllayer because cities that have 2 or 3 (or more) hulls have larger ecosystems and so more layers.
===Elbow on fraction of locations in hulls===