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Basic Principles

SimFinder uses a proprietary scoring engine that compares plans based on both price and network quality. We operate under the following principles:

• Only official sources: Pricing, data allowances, and conditions are taken directly from each carrier's official site. We do not rely on AI-generated information.
• Affiliate does not affect rankings: Whether or how much we earn in affiliate commissions has zero impact on scores. Our algorithm evaluates plans solely on price, data, and quality.
• Transparent update dates: Every plan records a last_verified_at field so you always know how current the data is.

How the Scoring Engine Works

1. Price Score

Based on the user's desired data volume and monthly talk minutes, we calculate each plan's predicted monthly price. This includes base price, data overage, voice option fees, and family discounts — i.e., the actual out-of-pocket cost.

2. Quality Score

We use public quality data from third-party sources (Opensignal, etc.). For MVNOs (virtual carriers), we apply a quality inheritance logic:

This design reflects MVNO-specific quality drops such as congested speeds during peak hours.

3. Voice Option Auto-selection

For the user's specified monthly talk minutes, we automatically choose the cheapest combination among each plan's voice options:

• per_call: e.g., "first 5 minutes free per call". Estimated at 3 min/call on average.
• monthly_total: e.g., "60 min/month free". Excess is billed per minute.
• unlimited: fully unlimited, no additional charge.
• No option: default per-minute rate applied (typically 44 JPY/min in Japan).

4. Bonus Score

• Data rollover supported: +3
• Family discount applicable (if requested): +5
• Exact data amount match: +5
• Unlimited plan for heavy users: +5
• Bonus cap: 10 points

5. Total Score Calculation

Total = PriceScore × (1 − qualityWeight) + QualityScore × qualityWeight + Bonus

The "quality weight" is user-adjustable via a slider (0–100). Lower for price-focused, higher for quality-focused.

Data Sources

We maintain an internal operations document (ops/data-sources.md) tracking the official pricing page URLs for 80+ carriers across 11 countries. Plan additions or updates always reference these official sources.

Network quality scores are based on public reports:

• Opensignal Mobile Network Experience Reports
• Japan Ministry of Internal Affairs and Communications — Telecom Market Verification Reports
• Each MNO's published coverage maps and technical specifications

Update Frequency & Verification

• Monthly: Re-verify major plans (MNO flagship plans, top MVNO staples)
• Quarterly: Full re-verification of all 11 countries / all plans
• Ad-hoc: Same-day updates when carriers announce pricing changes or new plans

Every plan JSON has a last_verified_at field indicating when it was last checked against the official source.

Frequently Asked Questions