I've just 'tweaked' the figures for Ethiopian Airlines, which routes via Brussels, and Singapore Airlines to reflect the actual number of seats that I understand are offered on their routes, as against the aircraft capacity which I had used in my chart.
On this basis we get the following:
Ethiopian Airlines - 57.88% (assuming Manchester is limited to 135 seats - available seats varies between 270-315 dependant on aircraft type)
Singapore Airlines - Houston - 63.33%(assuming Manchester is limited to 194 seats out of 253)
Singapore Airlines - Singapore - 74.62% (assuming Manchester is limited to 194 seats out of 253)
You also have to remember that freight can make a big difference as to how viable a route can be and, I am led to believe that Manchester almost fills the Ethiopian aircraft on each operation.