Methodology
Statistical Approach
The regression analysis on this page uses Ordinary Least Squares (OLS) to test whether global Brent crude oil prices can statistically explain movements in Philippine inflation. Because oil price changes take time to filter through supply chains before reaching consumers, the model uses a one-month lag — comparing this month's inflation against the prior month's oil price — rather than assuming an instantaneous effect. An initial two-predictor model also tested the PHP/USD exchange rate alongside oil price, but the exchange rate showed no statistically significant independent effect (p = 0.232) once oil was included, likely due to the two variables moving together; it was dropped in favor of a cleaner, single-predictor model without meaningfully reducing explanatory power. The final national model was then applied separately to each of the 13 major commodity groups, producing an individual coefficient, p-value, and R² for each — allowing a direct comparison of which categories respond most strongly to oil price changes. To validate the approach, the model's independently-computed year-over-year inflation figures were cross-checked against PSA's own officially published inflation rates and found to closely match, confirming the underlying calculations were methodologically sound before drawing conclusions from the regression results.
Building on the fitted national model, the dashboard also generates forecast scenarios to illustrate how inflation might respond under different oil price conditions. Rather than presenting a single, falsely precise prediction, each scenario includes a 95% prediction interval — the range within which the actual inflation rate could plausibly fall, given the roughly 60% of month-to-month variation the model does not explain (R² = 0.40). This interval is calculated as a genuine prediction interval, not a narrower confidence interval, since the goal is to estimate the plausible range for a single future observation rather than the average long-term relationship. Notably, the width of this interval remains roughly constant (approximately 6 percentage points) across all tested scenarios, indicating that the model's precision does not degrade meaningfully even at more extreme oil price levels within the range of historical data observed.