The Breakingviews Brexit Index uses nine data points to track the likelihood of UK citizens voting to leave the European Union when a referendum takes place. A rise in the index from its starting value in January 2015 of 100 suggests a greater likelihood of leaving the bloc.

The numbers used by the index have a two-month lag, reflecting the timing of data releases, but the result is designed to provide a leading indicator.

Three of the inputs are conventional economic indicators: monthly import and export figures showing the extent of UK trade with the EU; the value of the pound against the euro; and the European Commission's monthly gauge of UK consumer confidence. In each case, a higher reading is taken to mean a more economically content UK populace, less likely to vote for leaving the EU.

The next three metrics also rise in tandem with UK willingness to remain in the bloc. Monthly traffic from budget airline EasyJet offers a proxy for the extent to which Britons enjoy visa-free travel in Europe. UK government figures show shipments to the UK of German cars, and French Bordeaux wine.

There are three further inclusions. A rise in which suggests more Brexit risk. Monthly figures on asylum applications in the European Union, and the shift in monthly odds compiled by Ladbrokes, a top domestic bookmaker, are fairly easy to interpret. Lastly, the number of days on which stories involving migration or the European Union appear on the front page of the Daily Mail, the country's leading mid-market newspaper, acts as a proxy for the likely sentiment of "Middle England", the majority of Britons that do not live in London.

The data sets have been smoothed and weighted via standard deviations so that the more volatile series are not exaggeratedly represented in the final index. But they clearly involve judgment calls. You can tailor the index to reflect your own views, by selecting or deselecting the individual components.

For more interactive calculators and agenda-setting comment visit: BREAKINGVIEWS