The regional election in Catalonia on Sunday 27 September is considered by the pro-independence parties as the first step towards a gradual process that will ultimately lead to independence within 18 months.

Most recent polls remain too close to call, but even if the pro-independence parties win, greater autonomy remains more likely than independence given: 1) the Constitution prevents unilateral secession; 2) the Spanish government will never accept to lose a region that represents close to 20% of its GDP (and 16% of its population), and 3) the dramatic economic consequences of secession.

Nevertheless, a victory by the pro-independence parties would create substantial political and economic uncertainty. Medium-term, greater autonomy would put at risk the recent push for harmonisation and integration of the highly fragmented Spanish economy.

After the non-binding referendum on independence held last November, the Catalan pro-independence parties decided on a roadmap towards independence. The first step takes place on Sunday 27 September with the elections in Catalonia set up as a plebiscite.

All polls so far point to a lack of majority in terms of number of votes for the pro-independence parties. However, the result remains too close to call in terms of seats. Some polls point to a small seat majority (up to 6 seats) for the pro-independence parties Junt per Si ("Together for Yes"), the independence alliance formed by the centre-right CDC and the left-wing ERC, together with the radical-left CUP. However, in other polls, they would fall short of an absolute majority. In this case, the stance of Cataluña sí que es Pot (the local Podemos movement), which has been ambiguous about independence so far, will be decisive.

"We note that given the double-meaning of the vote, one should examine these polls with greater caution than usual, particularly as more than a quarter of the Catalan population remains undecided. However, if the pro-independence parties win the majority (however small), the new Catalan government is likely to proceed according to its roadmap set up at the end of March,and aim for independence by 2017",says Societe Generale.