wgeksl_fbmw {PriceIndices}

Extending the multilateral weighted GEKS-L price index by using the FBMW method.

Description

This function returns a value of the multilateral weighted GEKS-L price index extended by using the FBMW (Fixed Base Moving Window) method.

Usage

wgeksl_fbmw(data, start, end)

Arguments

data

The user's data frame with information about sold products. It must contain columns: time (as Date in format: year-month-day,e.g. '2020-12-01'), prices (as positive numeric), quantities (as positive numeric) and prodID (as numeric, factor or character).

start

The base period (as character) limited to the year and month, e.g. "2019-12".

end

The research period (as character) limited to the year and month, e.g. "2020-04".

Value

This function returns a value of the multilateral weighted GEKS-L price index (the GEKS index based on the Laspeyres formula) extended by using the FBMW (Fixed Base Moving Window) method. It measures the price dynamics between periods end and start and it uses a 13-month time window with a fixed base month taken as year(end)-1. If the distance between end and start exceeds 13 months, then internal Decembers play a role of chain-linking months. The month of the start parameter must be December. To get information about both price index values and corresponding dates, please see functions: price_indices or final_index. The function does not take into account aggregating over outlets or product subgroups (to consider these types of aggregating, please use the final_index function).

References

Gini, C. (1931). On the Circular Test of Index Numbers. Metron 9:9, 3-24.

Elteto, O., and Koves, P. (1964). On a Problem of Index Number Computation Relating to International Comparisons. Statisztikai Szemle 42, 507-518.

Szulc, B. (1983). Linking Price Index Numbers. In: Price Level Measurement, W. E. Diewert and C. Montmarquette (eds.), 537-566.

Lamboray, C.(2017). The Geary Khamis index and the Lehr index: how much do they differ? Paper presented at the 15th Ottawa Group meeting, 10-12 May 2017, Elville am Rhein, Germany.

Białek, J. (2022). The general class of multilateral indices and its two special cases. Paper presented at the 17th Meeting of the Ottawa Group on Price Indices, Rome, Italy.

Białek, J. (2022). Improving quality of the scanner CPI: proposition of new multilateral methods, Quality & Quantity, https://doi.org/10.1007/s11135-022-01506-6.

Examples

wgeksl_fbmw(milk, start="2019-12", end="2020-04")