wgeksgl_fbew {PriceIndices}

Extending the multilateral weighted GEKS-GL price index by using the FBEW method.

Description

This function returns a value of the multilateral weighted GEKS-GL price index extended by using the FBEW (Fixed Base Monthly Expanding Window) method.

Usage

wgeksgl_fbew(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-GL price index (the weighted GEKS index based on the geometric Laspeyres formula) extended by using the FBEW (Fixed Base Monthly Expanding Window) method. The FBEW method uses a time window with a fixed base month every year (December). The window is enlarged every month with one month in order to include information from a new month. The full window length (13 months) is reached in December of each year. The function measures the price dynamics between periods end and start. The month of the start parameter must be December. If the distance between end and start exceeds 13 months, then internal Decembers play a role of chain-linking months. 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.

Chessa, A.G. (2016). A New Methodology for Processing Scanner Data in the Dutch CPI. Eurona 1/2016, 49-69.

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

wgeksgl_fbew(milk, start="2018-12", end="2019-08")