We believe stagnant economic growth in European countries like Germany and Italy, where Carnival derives most of its guests for its AIDA and Costa brands, respectively, are reflected in these booking trends. Additionally, we believe Brexit may contribute to volatility in bookings and pricing for Carnival's U.K. brands. We believe that any modest pullback in U.S. consumer discretionary spending would drive lower net revenue yields in 2020 since North American customers represents just over 50% of Carnival's customer base. We believe lower net revenue yields from the North America segment would result in lower EBITDA growth than we are currently forecasting and translate to an EBITDA level that is not sufficient to offset rising debt levels to fund ship deliveriesas