Social historian Frank Snowden offers a very different route to an answer about Southern Italy in his meticulously researched and convincingly argued book, The Conquest of Malaria: Italy, 1900-1962: epidemiological, not economic.
We're used to thinking of malaria as a disease that besets Africa and other very poor places. We're used to thinking of Italy as a First World country, which we can visit without much worse risk than a pick-pocketing.
But the word "malaria" is an Italian word, a clue to the unsettling truth that until extremely recently, Italy was a country beset by this deadly disease. The last case of malaria in Italy was closed as recently as 1962. Deep into the 1940s, malaria sickened and killed Italians by the hundreds of thousands, even millions. A study conducted in 1882 found:
In a total population of twenty-five million … over eleven million people were permanently at risk. Of these, two million were infected, reinfected, or superinfected annually, and at least fifteen thousand died directly from the effects of the fever (a figure that later authorities … revised upward to one hundred thousand). Mortality from malaria varied from year to year, depending on the vagaries of rainfall and temperature, with fearful spikes every five to ten years, as in 1879, 1887, 1895, and 1900.
The life expectancy of farms in nonmalarial regions of Italy was 35.7 years on the eve of the First World War. In malarial zones, by contrast, the life expectancy at birth was only 22.5 years.
[In the least infected zone] 2.3 percent of the population reached the age of seventy-five in the 1880s, as opposed to a national average of 1.3 percent and 0.9 percent in heavily stricken Foggia and Rome.
Snowden quotes one Italian public health expert of the 19th century who compared Italy to the Sleeping Beauty of the fairy tale, which would not awake to modern life until malaria was overcome.
Nineteenth-century Italians did not know that malaria was spread by mosquitoes. But they knew that they were more likely to get sick on plains than up in hills, near water rather than in dry places, and at dawn and dusk rather than in mid-day. This knowledge shaped their lives in all kinds of poverty-producing ways.
[F]ully two million hectares were left totally uncultivated as a direct consequence of malaria, and further two million were cultivated badly. The height of the annual malaria epidemic in the summer coincided exactly with the peak of the agricultural season, when vast outlays of heavy outdoor labor were required …. To survive, farmworkers and peasants had to expose themselves to disease. But disease in turn entailed suffering, days of absence, and low productivity. For some, additional consequences were death and the immiseration of the widows and orphans they left behind. In addition, malaria prompted absenteeism by landlords and farmers, disdain toward manual labor, and an unwillingness to invest in agricultural improvement. It also encouraged peasants to live, if they could, far from the fields they cultivated. Thus, they arrived at work debilitated by disease or exhausted by the long trek from home.
All these problems most cruelly beset Southern Italy. The variant of malaria prevalent in Northern malarial zones like the Po Valley was enfeebling, but not lethal. Southern Italy had the climate to support the deadly form of the disease—a disease that (with excessive irony) took the life of Count Cavour, the conquerer of the South and the founder of the modern Italian state.
As late as 1918, the Ministry of Agriculture reported that "malaria is the key to all the economic problems of the South, and to the chronic difficulties of Italian agriculture."
Snowden describes the conquest of malaria as the greatest accomplishment of the Italian state—and by the time one finishes his book, one is convinced he is right. It was an Italian doctor who first charted the life-cycle of the parasite that causes malaria, and thus first predicted the course of the disease. It was Italian doctors who proved that the parasite was carried by mosquitoes. And it was these doctors, backed by the state, who launched the world's first national malarial program.
The story of that program is the story of modern Italian nationhood: early successes from the 1890s through the First World War, horrible retrogression under war and Fascism, culminating in a deliberate unleashing of malaria against the Italian population by the retreating German army in 1943-45—and then, finally, the tremendous progress of the postwar years, culminating in ultimate eradication. This eradication opened the door to real progress in the South—leaving only the question whether the South had been too debilitated by unhappy history to make use of its opportunities.