In the months after the Arab Spring, more than 64,000 migrants landed on the coast of southern Italy. Generally without valid immigration papers, marketable skills or a knowledge of Italian, most of them soon escaped the refugee camps in which they were placed in hopes of going to other E.U. countries such as Germany or Sweden. To make that trek, they needed both money and identification documents - probably forged - which left them at the mercy of the agrimafias that control migrant labor in southern Italy.

Winemakers in Sicily and Apulia took advantage of this cheap, undocumented labor, German economists Stefan Seifert and Marica Valente write in an academic paper released this year entitled "An Offer that You Can't Refuse? Agrimafias and Migrant Labor on Vineyards in Southern Italy." Their article is a rare academic study of labor practices that are pervasive not just in winemaking, but in all of agriculture. By one estimate, a quarter of Europe's agricultural labor is illegal or undocumented, Valente wrote in an email. The problem isn't limited to wine, or to Europe; in a 2016 report, Italy's Federazione Lavoratori Agroindustria pointed to "the exploitation of strawberry pickers in Huelva," a province in southern Spain, and the labor of "illegal immigrant children" in California.

Migrants who landed in Sicily, Apulia and Calabria were particularly vulnerable to exploitation. In Italy, as many as 500,000 immigrants may be "irregularly employed," according to the paper by Seifert, a research associate at the Institute for Food and Resource Economics and the chair of production economics at University of Bonn, and Valente, a graduate student at Humboldt University of Berlin and German Institute for Economic Research. About a third of agricultural employment in Italy and as much as 70% in Apulia is illegal, much of it supplied by a mafia-run system called caporalato in which gangmasters or caporali act as intermediaries between laborers and farmers.

A caporale typically keeps about half of a worker's daily salary of €30 for transportation, food, lodging and phone-charging, but such exploitative employment is the only way many illegal migrants can get a job and, eventually, a residence permit. The system goes back "a century or more," Valente wrote in an email. "It is a way to organise communities and their agricultural markets in a self-sufficient way."

Despite the high unemployment in southern Italy, Valente wrote, in many agricultural jobs, "Working conditions are bad, and wages are low. These are not jobs that many natives want to or can do." Agrimafias, she wrote, "are looking for illegal employment. People who are Illegally employed are easier to exploit. You can force them to stay under your control in unhealthy dormitories with safety hazards, you can enforce unpaid overtime and illegal deduction of wages and not pay social security."

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The migrants who came to southern Italy couldn't afford to stay in the refugee camps and detention centers where they were placed. Instead, Seifert and Valente write in their paper, as many as 93% of them escaped and entered the market for illegal labor. Because the labor wouldn't have been recorded, the two scholars couldn't measure its effects directly. Instead, they analyzed a range of data about wine production in Italy and France between 1999 and 2012 to concluded that labor productivity in the wine industries of Sicily and Apulia increased by 11% in 2011 and 2012, the two seasons immediately after the influx of migrants to those regions.

There was no apparent reason for that change - no technological innovations by winemakers, no significant change in demand for wine or prices paid for it, and no other changes in the labor market. Rather, the authors conclude that that the increased productivity in fact reflected "around 10 million unreported work hours, or 21,000 full-time employees" during each growing season and harvest.

The agricultural sector in much of western Europe has struggled to find enough labor since the 1960s as people have moved from farms to cities and often from south to north. In their book Chianti Classico: The Search for Tuscany's Noblest Wine, Bill Nesto and Frances di Savino note that mezzadri or sharecroppers provided much of the farm labor in the area through the 1960s. But in 1964 the Italian government banned the signing of new mezzadri contracts beginning a decade later. In that period, Nesto and di Savino write, "Sicilians and southern Italians helped to fill the gap. Later, non-Italian Europeans and Africans came to work."

Many European farmers have responded to the long-term decline in human labor by increasing their use of machines, but in Sicily, Valente wrote in an email, winemakers are often small producers and lag behind their peers in northern Italy in using mechanization. Still, she added, "Caporalato, this illegal system to recruit labor when needed, is diffused in all Europe. Not with this name, but the mechanism is the same."

According to a 2017 report by the Milan Center for Food Law and Policy (2017), 25% of European agricultural labor is illegal, with peaks of 60% and 40% in Portugal and Romania. Wealthy countries are not exempt; 40% of the labor in the Dutch tulip industry is illegal.

Germany and Austria are exceptions, with illegal employment in their agricultural sectors of 5% and 10% respectively. Enforcement of labor laws is stricter in those countries than in many others, Valente wrote in an email, but there are structural economic differences as well. Germany and Austria have much lower unemployment than Italy and smaller agricultural sectors that are more oriented towards grain, where harvesting is mostly mechanical, rather than grapes and other fruit, where manual harvesting is more common. And, she wrote in an email, "Austria and Germany did not receive sudden, large migrant inflows of so-called economic migrants, but of migrants who obtain asylum and financial support."

But all too often, lax legal enforcement is the response to "labor shortages due to emigration of local labor but with large inflows of migrants," Valente wrote in an email. "The two things together cause migrants to be employed, cheaply, and can allow many vineyards to survive."