What quantitative metric is most effective in assessing a business's current dependence on single revenue streams or client bases to guide strategic diversification efforts for disaster resilience?

The quantitative metric most effective in assessing a business's current dependence on single revenue streams or client bases to guide strategic diversification efforts for disaster resilience is the Herfindahl-Hirschman Index (HHI). The HHI is a widely accepted measure of market concentration, adapted here to evaluate a business's internal concentration of revenue. It is calculated by taking the percentage share of each individual revenue stream or client base, squaring each of those percentages, and then summing the squared results. For example, if a business earns 60% of its revenue from Client A and 40% from Client B, the HHI would be (60^2) + (40^2) = 3600 + 1600 = 5200. A "revenue stream" refers to a distinct source from which a business earns money, such as sales of a specific product line, service offering, or geographical market. A "client base" refers to a group of customers that contribute to the business's revenue, often categorized by size, industry, or relationship. The HHI effectively quantifies the degree to which a business's total revenue is concentrated among a few sources. Its value ranges from near zero, indicating a highly diversified revenue base with many small contributors, to 10,000, representing a complete dependence on a single revenue stream or client base (100% share squared). A higher HHI value directly indicates greater concentration and thus higher dependence on single revenue streams or client bases. This metric is most effective because it comprehensively accounts for the relative size and number of all contributing sources, not just the largest ones, providing a holistic view of concentration risk. For disaster resilience, which is a business's capacity to withstand and recover from significant disruptions, a high HHI signals severe vulnerability. Should a primary revenue stream decline or a major client face insolvency, the business's very existence is at risk. By calculating the HHI, a business gains an objective, numerical understanding of its concentration risk, which then directly guides strategic diversification efforts. Businesses with a high HHI are prompted to actively pursue strategies like developing new products, entering new markets, or acquiring new customers to intentionally reduce their reliance on existing concentrated sources, thereby lowering their HHI and significantly enhancing their resilience against unforeseen disasters.