In late 97 and early 98 the data levels out, but after that it resumes an upward pattern. They also have the largest ranges. The relationship between HGT96 and HGT97 will be stronger because they are closer together in terms of time. There is no obvious patterns between winning times and the year of the race. Steady rise in late 70's, and shot up in the 90's.
Track conditions do affect winning times.
The mean winning times excluding poor track conditions is lower, then when all times are included. There is no association between winning times and net amount of money paid to the winner. There is no association between the weight of the jockey and the net amount of money paid to the winner. It is hard to support this with data because there are only two different jockey weights. So it is hard to see a correlation.