According to the Irish Times last Saturday, Dublin port experienced a 6.3% increase in ferry tourism passengers in the first 9 months of the year, to over 1.4m. That's an increase of about 80,000 passengers. If you assume all of these were previous HSS passengers, then just over 50% of the traffic has been retained across all the other sailings, rather than the 75% I predicted. There could, of course, be other factors that I have missed.