The race is a tight one and has spawned a massive swathe of media analysis. This FT piece covers some of the implications for equities and bonds of a Brexit.

One of the conclusions is that not only might large UK exporters to the EU suffer but large EU exporters to the UK are the more likely to. On this analysis a hunt for arbitrage opportunities seems straightforward.

Software like ArbMaker will turn up big exporting pairs such as France’s Legrand SA vs the UK’s Spirax-Sarco Engineering plc (LG/SPX). Backtests will show the pair trades regularly and profitably.

However, the operational detail of such companies is important in the context of Brexit. For example, Legrand has a well-balanced export market with the UK representing perhaps 10% to 15% of revenue (it’s not broken out separately in the accounts). A weaker, Brexited euro may simply boost non-UK exports as well as mitigate any fall in UK sales that might happen along the lines suggested in the article.

Spirax-Sarco has parallels. Its Europe, Middle East and African division accounts for ~30% of operating profit. But the group has manufacturing sites in the EU. Those sites' top-lines, translated to sterling, would take a hit from a weaker euro. But their cost of goods numbers benefit. Given the weight of its other export markets untangling the aggregate impact is not straightforward.

Traders may thus end up concluding that the fundamental economic relationship between such companies will remain in place regardless of the Brexit referendum. If so, SPX/LG remains an attractive trade.

An alternative pair for dollar-only traders taking this view might be the US ETF pair EWU/EZU. That pair allow an aggregated approach to the thesis. EWU (fact sheet here) covers mid-size and large UK equities while EZU (fact sheet here) does the same for EU companies of member states within the monetary union.

ArbMaker analysis shows that the EWU/EZU trade has a historically lower profitability than SPX/LG - but that has come with a far lower level of in-trade volatility.

There is, of course, much more Brexit fodder to consider when scouring for arbitrage ideas. A few samples of the fare on offer can be found here, here and here.