User guide
The price index simulator lets you compute a personalised index, view its change since any year from 1997 onwards, and compare it with the overall Consumer Price Index (CPI) computed by Insee, as well as with the indices of 13 broad consumption categories.
The personalised index is computed from the amounts you enter for 13 broad consumption categories of goods and services.
The data you enter in this simulator is not sent to Insee.
Calculate a personalised index
You can compute a personalised index and view the curve of its change by editing the spending amounts associated with each consumption category.
The “Your expenses” section lets you enter, for each of the 13 consumption categories, an amount in the “Your value” field. Remember to specify whether the spending is monthly or annualised. Your personalised index curve adjusts and lets you compare it with the Consumer Price Index computed by Insee on the same principle, but using the average spending of all French households.
The “Average” column holds the average consumption spending of all households.
Next to each consumption category, a checkbox lets you display that category’s price index on the chart.
By default, your personalised inflation is compared with overall inflation from 1997 to today. You can adjust this period with the sliders in the “Period” section.
Understand which spending categories drive inflation
Once your personalised index is computed, you can tell whether you are more or less affected by inflation than the average French household. To go further, the “Breakdown” tab lets you identify the consumption categories that contribute most to your personalised inflation, comparing their contribution with the one observed for all households.
Calculation method and limitations
The personalised index is computed from the spending breakdown you enter and the price indices of the 13 broad consumption categories of the eCoicop V2 classification.
The indices of these categories cannot be aggregated directly. Indeed, the CPI indices are Laspeyres indices chained annually. For each year A, the simulator therefore first computes, for each consumption category, an index on a December A-1 = 100 base. These indices are then aggregated according to the spending breakdown you entered. The resulting annual indices are finally chained to build your personalised index over the whole period, on a principle comparable to the one used for the CPI.
The reference amounts shown in the “Average” column correspond to the average monthly spending per inhabitant within the scope of the consumer price index. They are computed from actual final consumption (including social security reimbursements), excluding imputed rents of owner-occupiers and life insurance charges (source: National accounts), divided by the French population (source: population census).
The personalised index is an estimate, with several limitations:
- Your spending breakdown is assumed to be constant over time. To compute the CPI, the weight of each consumption category is updated every year to account for changes in household consumption. In the simulator, the breakdown you enter is instead applied to the whole period;
- The computation is based on broad consumption categories. The indices of these categories are themselves computed from more detailed indices. Limiting the input to 13 categories keeps the simulator simple to use, but does not allow the exact composition of your spending within each category to be taken into account;
- The data used is rounded. The indices used for the computations are those published on insee.fr, rounded to two decimals. The weightings used are also those published on insee.fr, which are rounded and may therefore differ slightly from the exact values used to compute the CPI.
Because of these approximations, the index obtained using the amounts of the “Average” column is not strictly identical to the official CPI. Over a 30-year period, the gap remains below half an index point.
