📅 12 MONTH FORWARD VISIBILITY
📈 Demand Forecast
Seasonal Planner
Python SARIMA forecasting model trained on 3 years of retail sales data. Delivers 12 month forward demand estimates with upper/lower confidence intervals and a scenario toggle aligning commercial and supply chain forecasts in a single model. ✓ MAPE: 8.4%
36 mo
Historical Data Window
8.4%
MAPE (vs 23% manual)
±15%
Confidence Interval
€318k
Lost Sales Prevented (est.)
// live dashboard
Seasonal Demand Analytics
Category filter:
📈 3 Year Demand History with Seasonal Pattern units sold per month
Actual
Trend
±1 StdDev band
🌡 Seasonal Index by Month avg multiplier vs annual baseline
📊 Trend Component
🔁 Seasonal Component
📉 Residual / Noise
▶ Problem
- Seasonal demand spikes are consistently underplanned by 18 35%, leading to lost sales in peak months and expensive overstock in off peak periods.
- Finance teams and supply chain planners use entirely different numbers finance based on revenue targets, supply chain on last year's actuals plus a manual uplift.
- No statistical decomposition of demand signal: trend, seasonality, and noise are treated as a single undifferentiated number, making the forecast unpredictable.
- Manual forecast adjustments by category managers introduce systematic upward bias on average 12% above realised demand inflating purchasing plans.
▶ Solution
- Python SARIMA(2,1,2)(1,1,1,12) model fitted on 36 months of retail sales data per product category. Seasonal order 12 captures annual patterns; differencing removes non stationarity.
- Model decomposes demand into trend, seasonal index, and residual components, giving planners visibility into which part of demand is predictable vs genuinely uncertain.
- 95% confidence intervals (±15%) rendered as a shaded band on the forecast chart giving procurement teams a structured buffer range instead of a single number.
- Scenario toggle (base / optimistic / pessimistic) adjusts seasonal multiplier ±20%, enabling aligned planning conversations between commercial and supply chain teams.
▶ Key Findings
- The SARIMA model achieved 8.4% MAPE on out of sample test data versus 23.1% for the manual forecast process it replaced. A 14.7 point accuracy improvement.
- Apparel shows the sharpest seasonal peak: November December demand is 2.4× the annual average. This was consistently underplanned by 28% in prior years.
- Electronics demand has a strong secondary peak in August (back to school) equal to 75% of the December peak a pattern the manual forecast entirely missed for 2 consecutive years.
- FMCG demand is the most stable (seasonal index range: 0.88 1.14) and benefits least from sophisticated modelling a simple moving average outperforms SARIMA for this category.
- Promotional uplifts add an average 31% demand spike lasting 2 3 weeks. Incorporating a promotional flag as an exogenous regressor reduced forecast error during promo periods by 44%.
// projections
📈 12 Month SARIMA Forecast with Confidence Intervals
📉 Demand Forecast All Categories Combined solid = historical dashed = projected shaded = ±15% CI
Base scenario: Aggregate demand is projected to reach 42,800 units in December a 23% peak above the annual average, consistent with the 3 year seasonal pattern. The model predicts a strong Q4 driven by Apparel (+41%) and Electronics (+28%). Optimistic scenario (+20% seasonal multiplier) is appropriate if a major promotional event is confirmed for November historical promo uplifts support a December ceiling of 52,600 units. Pessimistic scenario assumes below average consumer sentiment, a mild summer, and no Q4 promotional investment projecting 34,200 units in December. Supply chain should plan procurement to the base scenario with a +15% buffer on A class SKUs.
// dataset
📊 Raw Dataset
Real data used in this analysis 50 rows shown. Download full dataset below.
| Date | Product Category | Units Sold | Revenue (€) | Promo Active | Season | Year | Month | Rolling Avg 3M | YoY Growth (%) |
|---|
// strategic guidance
💡 Advice for Companies with Similar Challenges
💡 Practical Recommendations
- Invest in seasonal decomposition modelling before your next peak season planning cycle. Even a simple SARIMA model fitted on 24+ months of data outperforms manual forecast adjustments by 30 40% on MAPE. The Python implementation takes one experienced analyst 2 3 days to build.
- Align commercial and supply chain forecasts in a single shared model not two separate spreadsheets. The act of sitting finance and supply chain around the same number eliminates the most expensive source of forecast error: departmental assumption gaps.
- Always show confidence intervals, not just a point forecast. A single number gives false certainty. A shaded band forces buyers and planners to think about range, which produces better safety stock decisions and more honest budget conversations.
- Treat promotional events as explicit regressors in your model, not as manual post hoc adjustments. A promotional flag variable with estimated uplift (drawn from historical promo data) typically reduces promotional period forecast error by 35 50%.
⚡ Key Takeaway
The most expensive forecasting mistake is not being wrong it is being wrong at peak. A SARIMA model trained on 3 years of data that reduces peak month MAPE from 23% to 8% on a €2M annual buy represents approximately €290,000 in avoided lost sales and overstock write offs. The model costs virtually nothing to build and run.