A diesel-price shock may be approaching Western economies. That's because the industrial fuel sits at the epicenter of freight, agriculture, construction, and heavy industry; soaring prices ripple quickly through supply chains, raising transportation and construction costs, reigniting food inflation, weakening consumer sentiment, and intensifying margin pressure on small and medium-sized businesses. The latest AAA data show that the nationwide average retail price reached $5.69 per gallon. That leaves diesel just below its April…