Methodology

Full transparency on how the Canadian Grocery Price Index is constructed.

Overview

The Canadian Grocery Price Index (CGPI) is a weighted Jevons price index computed from a fixed basket of 50 essential grocery products. Prices are collected daily from publicly available product listings on major Canadian retailer websites.

Unlike Statistics Canada's Consumer Price Index (CPI), which is published monthly with a 3-week lag, CGPI provides daily price tracking with same-day publication.

Index Formula

I_t = exp( Σ w_i × ln(P_it / P_i0) ) × 100

Where:

I_t — Index value at time t (base = 100)
w_i — Normalized weight of product i in the basket
P_it — Price of product i at time t (current period)
P_i0 — Price of product i at the base period

The Jevons index uses a geometric mean (via log-transformation) rather than the arithmetic mean used in a Laspeyres index. This has two advantages:

Substitution bias correction — The geometric mean naturally accounts for consumers switching to cheaper alternatives when one product's price rises.
Symmetric treatment of price changes — A 50% price increase and a 50% decrease offset each other (they don't with an arithmetic mean).

This is the same approach recommended by the ILO/IMF Consumer Price Index Manual and used by Eurostat for elementary price aggregates.

Basket Composition

The basket contains 50 products across 9 categories, weighted to approximate a typical Canadian household's grocery spending pattern.

Category	Weight	Products
Dairy & Eggs	15.0%	6
Meat & Protein	19.0%	7
Bread & Bakery	8.0%	5
Produce — Fruits	10.0%	5
Produce — Vegetables	10.0%	6
Pantry Staples	12.0%	7
Frozen	8.0%	4
Beverages	7.0%	5
Household Essentials	9.0%	5
Total	100.0%	50

Full Product List

#	Product	Category	Weight
1	2% Milk, 4L	Dairy & Eggs	3.0%
2	Butter, Salted, 454g	Dairy & Eggs	2.5%
3	Large Eggs, 12-pack	Dairy & Eggs	3.0%
4	Cheddar Cheese, Medium, 400g	Dairy & Eggs	2.5%
5	Greek Yogurt, Plain, 750g	Dairy & Eggs	2.0%
6	Cream Cheese, 250g	Dairy & Eggs	2.0%
7	Chicken Breast, Boneless Skinless, per kg	Meat & Protein	4.0%
8	Ground Beef, Lean, per kg	Meat & Protein	3.5%
9	Pork Chops, Centre Cut, per kg	Meat & Protein	2.5%
10	Bacon, 375g	Meat & Protein	2.0%
11	Salmon Fillet, Atlantic, per kg	Meat & Protein	3.0%
12	Canned Tuna, Chunk Light, 170g	Meat & Protein	1.5%
13	White Bread, 675g	Bread & Bakery	2.0%
14	Whole Wheat Bread, 675g	Bread & Bakery	2.0%
15	Bagels, 6-pack	Bread & Bakery	1.3%
16	English Muffins, 6-pack	Bread & Bakery	1.3%
17	Tortillas, Large, 10-pack	Bread & Bakery	1.4%
18	Bananas, per kg	Produce — Fruits	2.5%
19	Apples, 3lb Bag	Produce — Fruits	2.0%
20	Strawberries, 454g	Produce — Fruits	2.0%
21	Oranges, per kg	Produce — Fruits	1.8%
22	Blueberries, 1 Pint (312g)	Produce — Fruits	1.8%
23	Potatoes, 10lb Bag	Produce — Vegetables	2.0%
24	Onions, 3lb Bag	Produce — Vegetables	1.5%
25	Carrots, 2lb Bag	Produce — Vegetables	1.5%
26	Broccoli, per Head	Produce — Vegetables	1.8%
27	Tomatoes, per kg	Produce — Vegetables	1.8%
28	Romaine Lettuce, per Head	Produce — Vegetables	1.5%
29	White Rice, 2kg	Pantry Staples	2.0%
30	Pasta, Spaghetti, 900g	Pantry Staples	1.7%
31	Canned Tomatoes, Diced, 796mL	Pantry Staples	1.3%
32	Peanut Butter, 1kg	Pantry Staples	1.5%
33	Canola Oil, 946mL	Pantry Staples	1.5%
34	Granulated Sugar, 2kg	Pantry Staples	1.0%
35	All-Purpose Flour, 2.5kg	Pantry Staples	1.0%
36	Frozen Pizza, Pepperoni	Frozen	2.0%
37	Frozen Mixed Vegetables, 750g	Frozen	2.0%
38	Ice Cream, 1.5L	Frozen	2.0%
39	Frozen Chicken Nuggets, 700g	Frozen	2.0%
40	Orange Juice, 2.63L	Beverages	1.8%
41	Ground Coffee, 300g	Beverages	1.8%
42	Tea Bags, 72-pack	Beverages	1.0%
43	Coca-Cola, 2L	Beverages	1.3%
44	Bottled Water, 24-pack 500mL	Beverages	1.3%
45	Paper Towels, 6-roll	Household Essentials	2.0%
46	Toilet Paper, 12-roll	Household Essentials	2.0%
47	Dish Soap, 535mL	Household Essentials	1.5%
48	Laundry Detergent, 1.47L	Household Essentials	2.5%
49	Garbage Bags, 40-count	Household Essentials	1.0%
50	Chicken Thighs, Bone-In, per kg	Meat & Protein	2.5%

Data Collection

Retailers

Loblaws — Canada's largest grocery retailer
No Frills — Discount banner (Loblaw subsidiary)
Real Canadian Superstore — Large-format banner (Loblaw subsidiary)
Metro — Major Quebec/Ontario retailer
Food Basics — Discount banner (Metro subsidiary)
Sobeys — National full-service retailer (Empire Company)
FreshCo — Discount banner (Sobeys subsidiary)
Farm Boy — Specialty/local retailer (via Voilà delivery)

Method

Prices are collected from publicly accessible retailer websites. Product listings are accessed via the same pages any consumer can view, and price data is extracted from the server-rendered HTML.

Product Matching

Each retailer's product listing is matched to our canonical basket using a Tier 2 specification matching system:

Type match — Product category must match (e.g., "milk", "butter", "chicken breast")
Size verification — Package size must be within ±10% of the target
Variant matching — Specific variants checked (e.g., "salted" butter, "whole wheat" bread)

The cheapest available match is used for the index, reflecting actual consumer behavior where shoppers tend to choose store brands over national brands.

Update Schedule

Data is collected daily at 6:00 AM ET via an automated pipeline. The index is recomputed after each collection run.

CGPI vs StatCan CPI

Feature	CGPI	StatCan CPI (Food)
Update frequency	Daily	Monthly (3-week lag)
Formula	Weighted Jevons (geometric mean)	Modified Laspeyres (arithmetic mean)
Basket size	50 items	~700 items (food component)
Price source	Online listings (public)	In-store price collectors
Geographic scope	Ottawa (expanding)	National + provincial
Transparency	Full basket & methodology published	Basket weights published, individual prices not
Substitution bias	Lower (geometric mean)	Higher (arithmetic mean)

Limitations

Online prices only — In-store prices may differ, especially for produce and meat.
13 cities — Coverage spans major cities across Canada, but rural areas are not tracked.
No Costco or Walmart — Bot protection prevents automated price collection from these retailers.
50-item basket — StatCan tracks ~700 food items. Our basket may not capture all price movements.
No quality adjustment — If a product is reformulated, we track the price change but not quality changes.

These limitations are openly disclosed in the spirit of transparency. The index is designed to complement, not replace, official statistics.