question:
What is the avg revenue/margin improvement we deliver?

datasets:
- recurrency_customers.csv (30 rows): Customer master with customer_id, company_name, industry, go_live_date, is_active, plan_tier, employee_count
- recurrency_orders.csv (35000 rows): Order transactions with order_id, customer_id, order_date, total_amount, gross_profit, order_status, product_category, quantity

expected answer:
Average Improvement (comparing pre vs post go_live_date):
- Revenue per order: +12.6% improvement
- Margin (gross_profit/total_amount): +8.5% improvement
- Order frequency: +16.0% improvement

Strongest performer: Industrial Supply Co (+17.9% revenue, +13.7% margin) due to larger catalog and higher order volume as an enterprise customer.

Variance: Margin improvement has widest variance (std dev 4.3pp) across customers due to industry mix and product category differences.

Note: The order_date column has INCONSISTENT DATE FORMATS (mix of MM/DD/YYYY and YYYY-MM-DD). Must also EXCLUDE orders where order_status is 'returned' or 'cancelled'. Improvement must be calculated by comparing the SAME customer's metrics before vs after their go_live_date.
