But that signal goes unnoticed if the policy deadline is not really believed. And what happens when a difficult deadline hits?

This is precisely what is being played out in EU fisheries as we approach the landmark legal commitment under the Common Fisheries Policy (CFP) to end overfishing by 2020.

Transport back in time to 2009. Looking ahead to the reform of the CFP, the European Commission reflected on the state of EU fisheries in its green paper.

The assessment was bleak: "European fish stocks have been overfished for decades and the fishing fleets remain too large for the available resources."

Seizing this urgent opportunity for change, a broad coalition formed to push for ambitious policy.

They argued that while overfished stocks would take time to return to historical levels, we could stop overfishing immediately by setting appropriate catch limits and fishing less.

The economic case was clear. Because fish stocks have been depleted through decades of overfishing, taking a conservationist approach would increase the size of fish stocks and – perhaps counterintuitively – mean greater catches within a decade.

While NGOs were pushing for a deadline to end overfishing by 2015, the large fishing industry groups wanted a later date.

In the end the 2013 reform of the CFP had a requirement to end overfishing for all commercial fish stocks "by 2015 where possible and, on a progressive, incremental basis at the latest by 2020".

Pyrrhic victories

We are now approaching the end of 2018, but 'possible' apparently wasn't possible.

According to the most recent assessment, 40 percent of fish populations in North Atlantic, North Sea and Baltic are still being overfished.

In the Mediterranean and Black Sea that figure is closer to 90 percent.

This is not to deny the CFP deadline was going to be hard work, but that was the entire point: transitions, particularly fairly managed ones, often are.

If policy isn't challenging, it means it's just 'business as usual', which is some instances – like overfishing a common resource to the detriment of future generations and the ecosystem – is unacceptable.

Clearly, what makes the politics of this difficult is that it's fishers themselves who bear the brunt of the challenge.

Fishing is one of the most challenging occupations – mentally, physically, financially – and remains the most dangerous.

The medium to long-term benefits of ending overfishing massively exceed the costs, but the short-term loss of income forces the fishing lobby to fight necessary change.

The current record profits in the fishing industry, while distributed unevenly, is a buffer to making reductions in fishing.

Unfortunately as we approach the 2020 deadline, member states are calling for a new process of assessment of the costs of complying with it at this short notice.

This may not produce cheery numbers; as anyone who has tried to get an emergency locksmith knows, the less time you have to do something, the more it costs.

This is why early action is preferable (as researchers have found), and it shows us that even if the economic analysis is done correctly (ie a consideration of both the costs and the benefits over an extended time period) the decision of when to do it is political.

Breaking cycle of delay, protest, postpone

Putting off action for so long that it becomes ever more 'costly' to comply creates moral hazard – where excessive risks are taken in the knowledge that the costs will be borne on someone else.

If the landmark 2020 deadline isn't met, why would any other policy in the Common Fisheries Policy be trusted?

Or what about other EU policies? You can be sure that other industries with something at stake in EU policy-making are watching fisheries with interest.

There is no hope for ambitious policy-making if there is no trust in the policy signals being sent.

There is a dangerous cycle of delay, protest, and postpone that not only fails policy objectives but undermines trust in political institutions.

As fish stocks in the deep sea have their fishing limits set on a two-year basis, this coming November is crunch time to see if the 2020 deadline and EU policy really means something.

Griffin Carpenter is a senior researcher at the New Economics Foundation