The quality of a bottle of wine depends upon the quality of the grapes used as well as the techniques used by the vintners. The techniques used by the major wineries do not change very frequently. For example, over the last 30 years the makers of Hill of Grace wine have only introduced one significant change in their wine making process. In contrast, the quality of the grapes used from year to year varies according to weather conditions during the growing period, up until the time that the grapes are picked. This is particularly true for red wines.
To make it even more complicated many icon wines, such as Grange Hermitage, use blended grapes (grapes taken from a variety of different regions in South Australia). Using a blended grape increases the complexity of predicting a good vintage as growing conditions in each region as well as the proportion of grapes taken from each region need to be taken into consideration. An “average growing conditions” needs to be calculated based on information available. Other icon wines, such as Hill of Grace, only take grapes from one property which makes prediction of quality from year to year a little easier.
Some of the key factors that need to be taken into consideration during the growing season are:
The minimum and maximum temperatures each day; and
Analysis of the impact these key variables can have on price can be looked at by collection price data from Auction houses. One such paper that has done this is by Danielle Wood looking at What Determines the Future Value of an Icon Wine? Evidence from Australia. Of course if you are importing wines from Australia you also have to consider foreign exchange terms as the Australian dollar has moved up against most cross currencies when looking at Forex Trading Platforms.