Under stocks to sell, Walgreen is the class of the drugstore sector, but is that enough anymore? For years, demographics played to the sector�s strength: As the population aged, more people went to drugstores to fill prescriptions and buy over-the-counter medicines. That increased foot traffic and added to growing sales of the non-drug items that, with their higher margins, pump up drugstore profits. But the squeeze on health-care costs -- especially drug costs -- is now a strong trend working against demographics. Increasingly, corporate insurance plans are forcing workers into mail-order drug programs. Over the long term, this new trend will cut the foot traffic so critical to drugstore profits.