Sydney to Hobart yacht race winning times

The Sydney-Hobart yacht race starts from Sydney Harbour on Boxing Day (26 December) and finishes several days later in Hobart. It is a 630 nautical mile ocean race. Here are the winning times for 1945 to 2004.

The data for 1945-1993 comes from the Sydney Morning Herald (24 December 1994). The more recent data are from the official race website and the Sydney Morning Herald. The data originally published included an error in the 1965 results; it has been amended here.

The winning time (first across the line) varies quite a bit due to weather and improvements in boat design and sailing techniques. What has been the pattern of improvement over time?

Winning times have generally decreased, from around 6 days to around 2.6 days on average.

How can we describe the pattern further? Using statistical methods to put a straight line on the graph (regression) gives this:

One way to describe the decrease is with a straight line. The straight line above was fitted by linear regression, giving time in days = 99.0 - 0.0482 x year. This describes the decrease quite well.  However, we should be cautious about applying this model to future races. For instance, extrapolating indicates that by the year 2030 it will take, on average, around 1 day to win, and by the year 2058 the winning boat will arrive before it leaves!

Are there other ways to describe the changes?  Another alternative method fits lines to only parts of the data and joins the results, like this:

This type of method allows for some curving by fitting straight lines to subsets of consecutive years. It makes some other adjustments and is known as 'locally weighted regression', or 'lowess' for short. The lowess curve is shown above. It shows that after about 1975 the rate of improvement slowed down.  The lowess curve helps visualize the changes over time, but it does not give us a formal mathematical model of the change over time.