Ferry traffic on the northern routes plunged after the Queen of the North sank and has yet to rebound to its pre-sinking level, according to statistics in a traffic demand forecast just completed for BC Ferries.Northern traffic was steady in the three years before the Queen of the North incident at around 130,000 per year or a bit less. Traffic plunged to 94,000 for the 2006-07 year, when the northern summer schedules were reduced due to the loss of one ship. They bounced back to 120,000 the following year when the normal schedule was restored. But in 2008-09 traffic declined to 110,000, and dropped a bit more in 2009-10 to 106,000.The consultants hired to write the traffic forecast, InterVISTAS Consulting Inc, note that it is challenging to predict how many passengers and vehicles will travel on BC Ferries in the future, and that the northern routes are particularly difficult to forecast.In general, the report says, the northern routes are much more sensitive to price than the other ferry routes, with fewer passengers travelling as prices rise."This is perhaps not surprising as many of the voyages on this route group are longer and of higher price than the southern routes," the report states. The consultants' analysis of the available data found that traffic on the other routes, which make up the vast majority of BC Ferries's business, is not extremely sensitive to price increases.Another challenge for forecasting is that the north has the lowest traffic levels of any of the BC Ferries routes."Low levels of traffic are always problematic for forecasters as there typically is greater variation from year to year whereas higher traffic levels tend to smooth out variations in demand," the report notes.The consultants forecast a small increase in traffic over the next few years (to about 119,000 in 2016), but say it is also possible that traffic will decrease, not grow at all, or increase to higher levels. (The report includes complicated percentile predictions for several outcomes.)The report, titled "Performance Term 3 Forecast and Measurement of Demand Elasticity for British Columbia Ferry Services Inc." and labelled "confidential" is now available on the BC Ferry Commission website.