Quantified Self: a year of grocery data

I started tracking our grocery expenses when we decided not to sign up for a community-supported agriculture program. I’d tracked several seasons of the CSA, and I wanted to see if we would still eat lots of vegetables without the bi-weekly commitment of a farm share. I also wanted to get a sense of what we bought.

I started scanning my receipts, and I found an assistant who could type them in. I set up a spreadsheet where he could type in the dates, stores, and line items (including quantity, unit price, and total). There were occasional typos, but I could find and fix them. I used a look-up table to match the line items with friendlier names (ex: RDPATH SUGAR is white sugar) and file them under categories.

The data below isn’t complete because there were a number of receipts that slipped through the cracks. If I let too much time pass between data updates, I couldn’t remember what some things were. Still, it should give a general idea of how the year went. The data covers April 2012 to March 2013 and includes 1223 line items.

Here are some questions I wanted to explore:

  • A. How much did we spend in various categories, and how does that vary month by month? For example, how much do we spend on vegetables? Is this in line with what we want our diet to be?
  • B. What items do we spend the most on? This could point to better ways to economize (buying in bulk, finding cheaper choices) or show us where it’s worth spending on better quality because we use so much of it.
  • C. How frequently do we buy certain items? Can we predict consumption patterns or sale patterns, and stock up when things are on sale?
  • D. What are the normal prices and the sale prices for various items? When and where does it make sense to buy different things?

So, let’s see! Click on the images to view larger versions.

A. How much did we spend in various categories, and how does that vary month by month?

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Grocery expenses worked out to be $422/month for this family of three in Toronto, Canada. We ate pretty well, enjoying our favourite foods, the occasional snack, and fresh fruits and vegetables, and buying organic milk (which turned out to be a large part of the budget, but probably worth it). Because we cook in bulk, some months have larger grocery bills and some months involve more freezer-raiding. The standard deviation was $160.

We spent the most on meat ($59/month) and dairy ($53/mo), but fruit ($47/mo) and vegetables ($46/mo) also made a respectable showing. Vegetables worked out to $22 every two weeks, which is less than what we were paying for the CSA box. That could be accounted for as a pricing difference between conventional and organic produce, and we still bought extra vegetables when we were in the CSA. Paying attention to our increasing vegetable spending helped us learn lots of ways to prepare food. Yakiudon turned out to be a house favourite, and other stir-fries are great too. We haven’t been able to get our vegetable spending to overtake meat, but that’s probably because of the occasional indulgence in lamb korma.

The month-by-month pattern made me think there were bigger differences, but because stocking up and bulk cooking means our monthly patterns probably aren’t a good source of information. Our vegetable spending is positively correlated with our overall grocery spending (0.7), which means that ~50% of the ups and downs are explained by the ups and downs in our grocery bill (maybe we just bought less).

Anyway, I feel pretty good about how the proportions worked out. There’s hope for us yet!

B. What items do we spend the most on?

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We buy milk because J- likes it. It turns out that Canada prohibits the use of artificial growth hormones for dairy cows and antibiotics are also controlled, but we still get the organic version for extra safety. Lamb shanks from the butcher are a splurge when it comes to making lamb korma. We found that Metro often has the lamb cuts we want, though, so we check there first now. Shrimp sees a lot of use in pad thai, stirfries, and other wok-based dishes, plus our occasional wonton marathons. My standard breakfast is rice and fried egg, and we use lots of eggs in baking and stirfrying too. I was surprised that much butter (and we do, even though we try to stock up during sales!) because of baking, and that grapes made it into our top ten despite being something we don’t eat that often. We buy grapes only when they’re super-crisp, and sometimes we forget to eat all of them before they soften. Also, we usually buy chicken legs or drumsticks, but it was interesting to see that whole chickens turned up on this list even though we don’t buy them frequently.

C. How frequently do we buy certain items?

A block of butter, a carton of 18 eggs, and a bag of 4L milk every 1.5 weeks (eggs and milk feel more frequent than that, though…)
A 2kg bag of white sugar every ~2 months, a 1kg(?) bag of demerara sugar every ~6 months

It’s a little harder to tell how often things go on sale and how much we want to stock up, because we skip sales if we still have stuff in stock (ex: butter) and we shift our buying patterns depending on what’s on sale (ex: 30% on a particular meat package that’s nearing its best-by date). It looks like butter is always good to get on sale, though, and that seems to be every other month.

D. What are the normal prices and the sale prices for various items?

Hmm, I think it might be useful to remember which ones sometimes go on big sales, so then it makes sense to postpone until things are in season.

Butter is usually $4.97, sometimes $2.88. Salami is sometimes $4.20 off ($5.29), clementines are sometimes $3 off ($3.99), and bacon is sometimes $2.58 off ($2.97). Sometimes we can get Japanese udon noodles for $1 instead of $2.19. And then there was that time that Campbell’s condensed chicken soup was on sale for $0.50 instead of its usual $0.97, and we bought a lot. =)

In general, our neighbourhood No Frills supermarket has pretty prices for stuff, although some things necessitate a special trip to the Sweet Potato organic food store or the Welcome or Oriental Harvest ethnic supermarkets. Metro also stocks some sauces and lamb cuts that are hard to find elsewhere. I sometimes look up prices from my records, but the difference is usually pretty small.

 

So that’s roughly a year of data. Hmm… Should I continue? Maybe I’ll scan and stash the receipts, but I might not have someone type in the information until I have more questions I want to ask. It was interesting to collect that data over a decade, though!

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