Why have historians ceded authority to economists as reliable and competent policy advisors?

Since the 18th century historians have advised policy-makers. Then, about fifty years ago, economists have taken their place. Why did it happen and what can be learned from this occurrence?
During the last 15 years, economic sociologists, historians and sociologists of economic thought have contributed excellent and enlightening researches (many of which were featured in our community) on how neoliberal or neo-classical economists have achieved their special status as reliable and competent policy advisors. But that is only one part of the story.
According to noted historians David Armitage and Jo Guldi, historians ceded authority to economists by losing their long-term (“longue durée”) perspective. They stopped studying broad stretches of time, refused to analyze long-term trends over centuries or even millennia. Instead, they gave in to “short-termism,” focusing on obscure moments in time that weren’t relevant to the public sphere.
When historians first became professionalised in the late 19th century, it was still possible for them to tackle subjects of genuine breadth and ambition. A recent survey of some 8,000 history dissertations written in the US has shown that the average period covered in 1900 was about 75 years; by 1975, that had shrunk to about 30 years.
economics history And as historians became enchanted with micro-histories, from about the middle of the 20th century economists were expanding the reach of their discipline. Long-term narratives sought by policy makers in an age of ‘limits to growth’ and the ‘population bomb’ have begun to be offered also by from think tanks, demographers and futurologists. But theirs long-term narratives were ‘dirty’, produced more for present purposes than for its critical stance towards contemporary pieties. These non-historians dealt with an impoverished array of historical evidence to draw broad-gauge conclusions about the tendency of progress.
The crucial point I take from Armitage and Guldi’s fascinating analysis of the transformation of history as a profession concerns the short-termism applied since the 1980s in contemporary mainstream economics. Focusing on the increasing short-termism in economic and business research, neoliberal economists embody an inability to break this gridlock which undermines attempts to address real-world issues and policy challenges that are deeply historically embedded.
In general, short-termism has no defenders, everyone seems to be against it. But those who mainly serve, and perceived, as proper policy advisors are still economists. If this will not be changed, we all are going to pay the price– in fact this costly price already paid by everyone since the “merry” 1980s.
Armitage and Guldi conclude their article titled “Bonfire of the humanities” asserting: “The return to the “longue durée” is not just feasible, it is imperative: feasible, because of the resources to hand and the means to make sense of them; imperative, because of the proliferation of big data in every aspect of our lives and the necessity of fighting back critically against those who might wield its powers of shock and awe against us. The world might have shrunk but the collective challenges facing its people have grown only more apparent, in all their complexity. At a time of ever-expanding inequality – within societies, if not between them – when international institutions have reached breaking-point; and when anthropogenic climate change threatens our water and our food, our political stability and even the survival of our species, even the most basic apprehension of our condition demands a scaling-up of our enquiries.”
Proponents of alternatives must rise up. They are not in short supply; they are even in high demand. History is an illuminating projector towards the future. Understanding political economy, which is essentially a historical science, is a powerful tool to confront neoliberal politics backed by neoliberal economics.