Method and formulas

The sources and their rhythm

All data comes from public bodies, with no key or subscription. A script re-reads it every day at 06:17 UTC and only changes the data file when a figure has moved. Last change: 9 October 2026.

Quarterly debt

TodayINSEE · Q2 2026

Maastricht debt of all public administrations, in euros and as % of GDP, 2020 base. Published about three months after each quarter ends; next release expected late December 2026.

Annual debt and deficit

TodayEurostat · 2025

Table gov_10dd_edpt1 from 1995; before 1995, INSEE national accounts, 2014 base. Small series break in 1995. Eurostat revises twice a year, in April and October.

Spending, revenue, interest, functions

TodayEurostat · 2025

Tables gov_10a_main (spending TE, revenue TR, interest D41PAY) and gov_10a_exp (spending by COFOG function). Same tables for the 27 member states. A year’s totals arrive in April of the next year; the breakdown by function, transmitted twelve months after year end, comes a year behind the totals.

10-year yields

TodayECB · August 2026

ECB IRS series, monthly average of 10-year government bond yields for France, Germany, Italy, Spain, Greece, Portugal and Belgium.

Population and employment

TodayEurostat · 2026 / 2025

Population on 1 January (demo_gind) and persons employed in the national-accounts sense (nama_10_pe). Updated once a year.

Negotiable debt, ratings, holders

TodayAFT, Banque de France · by hand

Outstanding and average life of negotiable State debt, the financing programme and the ratings table come from Agence France Trésor; the non-resident share from the Banque de France. No API: these figures are copied by hand each month, with their date.

Prices, gold, Livret A, shares (what €100 became)

TodayINSEE, Eurostat, World Bank, Euronext, Damodaran · 2025

Prices: INSEE franc-euro converter (purchasing power since 1901) chained to the 2015-base price index. Ten-year State yield: Eurostat irt_lt_mcby_m (Maastricht criterion, since 1980). Gold: World Bank monthly price in dollars (“Pink Sheet”, CC BY 4.0), converted with Eurostat franc/ECU and dollar/ECU rates (ert_h_eur_m, ert_bil_eur_m) until 1998, dollar/euro after. Livret A: list of rate changes (Banque de France, Caisse des Dépôts), kept by hand in src/data/livret-a.json, updated 9 October 2026. French shares: year-end closes of the CAC 40 and CAC 40 GR (gross dividends reinvested) published by Euronext, copied by hand into src/data/cac40.json, updated 9 October 2026. US shares: yearly S&P 500 return with dividends and year-end levels from Aswath Damodaran’s public file (NYU Stern), converted into euros at the December rate.

Stability programmes

TodayCompiled by hand

The deficit paths promised since 1998 are taken from each programme, with a link to the source document per vintage. They do not refresh automatically: the new programme is added each spring.

The formulas

Every derived figure on the site is a simple operation on the series above. The examples are computed with today’s data.

Real-time estimate

Formuladebt(t) = latest official figure + g × seconds elapsed since the end of the quarter

Today€3,595.5bn + €5,650/s since 30 June 2026

g extends the rise of the past twelve months: (debt Q2 2026 − debt Q2 2025) ÷ (365.25 × 86,400 s) = €5,650 a second. It is a linear estimate; the real debt moves in steps (issues, redemptions, seasonal revenue). The true figure is only known at the next release.

Rise over a year

Formuladebt Q2 2026 − debt Q2 2025

Today€3,595.5bn − €3,417.2bn = €178.3bn

Per inhabitant

Formuladebt ÷ population on 1 January

Today€3,595.5bn ÷ 69.1 M = €52,024

Babies included. Nobody has to repay that tomorrow; it is a way to measure the size of the debt.

Per person in work

Formuladebt ÷ persons in employment

Today€3,595.5bn ÷ 30.6 M = €117,354

Unemployed people, pensioners, children and students are not counted.

Months of output

Formula% of GDP × 12 ÷ 100

Today119.0% → 14.3 months

GDP is the value of everything the country produces in a year.

Primary balance

Formulapublic balance + interest paid (as % of GDP)

Today-5.1% + 2.2% = -2.9%

The balance before interest: what the budget would do if the debt cost nothing.

Average rate paid on the debt

Formulainterest of the year ÷ debt at the end of the previous year

Today2025 : 2.02%

An approximation of the “apparent” rate: the State pays a different rate on each loan depending on when it was issued.

Interest per €100 of revenue

Formulainterest ÷ public revenue × 100

Today€66.6bn ÷ €1,562bn × 100 = €4.27

Spread over Germany

FormulaFrench 10-year yield − German yield, in basis points

Today4.00% − 3.19% = 82 bp

One basis point is 0.01 percentage point.

The simulator

Formuladebt(t) = debt(t−1) × (1 + r) ÷ (1 + g) − primary balance(t)

TodayStart 2025: debt 115.6%, average rate 2.02%, primary balance -2.9%

All as % of GDP. r is the average rate paid, which converges to the market rate at 1 ÷ maturity a year (default maturity: 8 years). g is nominal growth: (1 + real growth) × (1 + inflation) − 1, 3.2% by default, using the 2016–2025 averages (1.3% real, 1.9% inflation). The default market rate is the latest 10-year yield (4.0%). Spending and tax measures phase in over 5 years. No feedback: measures don't change growth, debt doesn't change rates.

Rate paid minus growth (r − g)

Formulaaverage rate paid − nominal GDP growth of the year

Positive, interest runs faster than the economy and the debt rises even with a zero primary balance; negative, growth lightens the debt. The “market rate” version swaps the rate paid for the latest 10-year yield and growth for the simulator’s long-run average.

Debt-stabilising balance

Formuladebt × (r − g) ÷ (1 + g)

Today0.9% of GDP, an effort of 3.8 points

The primary balance that would hold the debt constant as % of GDP once the whole debt pays the market rate.

What €100 became

Formulaprices(t) = 100 × index(t) / index(start) · gold(t) = 100 × price(t) / price(start) · shares(t) = 100 × dividends-reinvested index(t) / index(start) · Livret A(t) = Livret A(t − 1) × (1 + the year’s average rate) · bonds(t) = bonds(t − 1) × (1 + mean of the ten-year yields of the last ten purchase years)

Annual averages for prices, gold and yields, year-end values for shares; the chart uses a logarithmic scale. Bonds form a ladder: at the start the whole sum is placed at the year’s ten-year yield; each following year one tenth is reinvested at the yield of the moment and held to maturity, with interest reinvested. No fees or taxes, except the Livret A, which is net. The “purchasing power” column divides the end value by the rise in prices since the start. Rate-sensitivity example: a ten-year bond bought at par in 2021 (0.0%) and valued in 2023 at 3.0% is worth 21% less, by discounting the remaining coupons and repayment.

Promises kept

A “promise” is the first forecast year back within 3% of GDP after the last year above it, in a given programme (or the first forecast year, if the year before was above 3% as known at the time). It is judged on the figure first published the following spring, as France was assessed at the time, not on today’s revised series. A “postponement” is a later target set while the previous one was missed or not yet due.

European ranks

Ranking of the 27 member states on the year’s Eurostat value, highest to lowest. The “deficit” is minus the public balance. “Breaking both rules”: debt above 60% of GDP and deficit above 3%.

Known limitations

The estimate is linear

The debt does not rise at a constant speed: financing needs are concentrated in the first half of the year and the Treasury often slows issuance towards year end. Between two releases the gap with the final figure can reach a few tens of billions.

Divisors are annual

Population and employment update once a year, so per-inhabitant and per-worker figures use today’s debt and the year’s divisor.

Accounts get revised

INSEE and Eurostat revise past years, sometimes by several tenths of a point of GDP. Charts show today’s series; the targets page also shows the figures as first published.

The simulator gives orders of magnitude

It forecasts nothing. It applies an accounting identity to visible assumptions, with no effect of fiscal policy on growth or of debt on rates.

Programmes are compiled by hand

Each vintage links to its source document; a transcription error remains possible and is corrected on report.