In a historical simulation with a 500-day historical reference period, the 500 historical daily changes (from Day 0 through Day 500) are used to create 500 scenarios for what might happen between today and tomorrow (on Day 501). In practice, the risk factors that may be used in a historical simulation are divided into two categories: those where the percentage change in the past is used to define a percentage change in the future, and those where the actual change in the past is used to define an actual change in the future. Stock prices are usually considered to be in the first category, while interest rates are usually considered to be in the second category. The historical change in the stock price from Day 0 to Day 1 should therefore be measured as a $72 / 76 - 1 = -5.263\%$ change, while the change in the interest rate should be measured as a $2.60\% - 2.50\% = 0.10\%$ change. Applying these changes to the current stock price and interest rate of HKD 94 and 3.8%, respectively, produces a scenario for the historical simulation with a stock price of $94 * (1 - 0.05263) = \text{HKD } 89.05263$, and an interest rate of $3.80\% + 0.10\% = 3.90\%$.*