Method
Subsidy per backer is actual shipping plus packaging/handling minus shipping charged after the entered fee. Region totals are weighted by entered backer counts.
Limits
Keep product fulfillment separate from shipping charges to avoid double-counting. Taxes, address changes, and carrier rates are not calculated.
Related tools
Separate shipping charged from shipping recovered
For every region, actual shipping plus packaging/handling is compared with shipping charged after the entered percentage fee. Backer count weights each regional result, so a small international group can still materially affect campaign contribution.
Use the result in a design decision
A positive subsidy is creator cost; a negative value means the entered charge recovers more than actual shipping plus fee. Use a fulfillment quote for each region and do not assume the model predicts carrier rates or tax treatment.