Index calculations

Unit guard before the calculation

Before every division we verify that the net wage is in euros per month (EUR 10-3000) and the gyro price in euros per item (EUR 0.005-25), ruling out drachma/euro or cent mix-ups.

51/51 years pass the unit guard

The calculation pipeline

1. 1. Wage: gross minimum wage of the year -> social contributions (year-specific rate) -> income tax on a 14-payment basis -> net monthly wage (exact -> rounded to cents).
2. 2. Price: observations and anchors are normalized geographically (Athens / 1.08) and by channel, converted to euros (/ 340.75 in the drachma era), filled by interpolation under the selected CPI mode, adjusted for price regulation (x1.2 in 1976-1985) and, when enabled, rescaled to the classic gyro composition.
3. 3. Index: quotient = net wage / price, index = quotient rounded to the nearest integer. The result reads as "how many gyros the wage buys".

Special cases and adjustments

• Regulated era 1976-1985

  Recorded prices of this period are state-regulated, not free-market. A ×1.2 (+20%) uplift is applied to approximate street prices, and the uncertainty band widens to ±35%.

• Athens-based sources (e.g. Pagrati)

  Prices from Athens outlets are divided by the geographic premium 1.08 (+8%) before entering the model, so the index tracks the national average rather than expensive districts. The same applies to user reports.

• Single-source years

  When a year is documented by a single reference (e.g. one article), confidence is downgraded to "B" and the uncertainty band widens to ±15%. The table shows a "1 source" badge.

• Derived and pre-anchor years

  Years without a direct observation are produced by weighted interpolation between anchors and the catering CPI (±20% band). Before the first 1976 anchor, projection runs backwards with a ±25% band. Documented years keep ±10%.

• Drachma-euro transition (2002)

  All prices and wages are converted to euros at the fixed rate of 340.75 GRD/EUR before any division. The unit guard rules out drachma, euro and cent mix-ups.

• Net wage with 14 payments

  The monthly net wage is derived from gross by deducting social contributions and the year's income tax, with a 14-payment annual income spread over 12 months (bonuses). The index therefore measures actual disposable income.

• Classic-equivalent rescaling

  Historically the gyro was smaller and came without fries. Equivalence is 0.7 x (meat grams / 88) + 0.30 x composition, and the price is multiplied by 1/equivalence. The index then always counts today's classic gyro (meat cost base 0.65).

• Borderline rounding (±0.5)

  The index is rounded to the nearest integer. When the quotient's fractional part sits within ~0.05 of 0.5, the row is flagged "borderline": a tiny input change would shift the index by 1. If wage/price rounding moves the index by ±1, a "from rounding" badge appears.