(Decanter) - Data from estate agency Knight Frank shows that Sonoma in California has seen some of the steepest rises in vineyard prices. See the charts below for more details.

Napa Valley might have spearheaded California's emergence on the world wine scene in the past 40 years, but it is neighbouring Sonoma that appears to have seen stronger interest in vineyard acquisitions in the last couple of years.

Vineyard prices across Sonoma County were up by 18% for the year to the end of June 2014, according to estate agency Knight Frank's latest global vineyard index.

As the graphic above shows, Hawke's Bay in New Zealand and Barossa in Australia were close behind, rising by 17.6% and 14% respectively. Perhaps surprisingly, Bordeaux and Burgundy vineyard prices remained level over the period, suggesting that they may have reached a plateau.

The second chart below represents the percentage of wealthy individuals around the world who showed interest in buying a vineyard. Knight Frank interviewed wealth advisers with a collective 30,000 'ultra high net worth individuals' on their books.