How much of the Irish population relied heavily on potatoes before the Great Famine?

By the early 1840s, it is estimated that almost half of the Irish population depended almost exclusively on the potato for their diet. This reliance was particularly acute among the rural poor, including landless laborers known as cottiers, for whom potatoes provided approximately 80 percent or more of their total caloric intake. While the rest of the population also consumed large quantities of the crop, the extreme dependence of the rural peasantry on one or two high-yielding varieties left the country highly vulnerable when late blight destroyed the harvests between 1845 and 1849.123