US candle market retail sales and USPS package volume achieved a 0.97 correlation between 2005 and 2022, which makes one wonder how many of those packages contained candles, and whether the postal service has been, in some ineffable way, delivering the ambient lighting market to itself. The candle, that ancient technology for producing light while also smelling like 'Autumn Harvest' or 'Sea Breeze,' grew into a multi-billion dollar industry over this period, presumably because people kept ordering them online and having them shipped. The USPS, for its part, arrived reliably, if occasionally singed.
Both metrics grew substantially through the 2010s, with the US candle market expanding from roughly $2 billion in the mid-2000s to over $3.5 billion by 2022, and USPS package volume growing from under 3 billion packages annually to over 7 billion by the pandemic peak. The e-commerce revolution is the shared engine: as online retail grew, USPS package volume grew with it, and candles — being a popular gifting and self-care product — were among the categories that migrated heavily to online purchasing. The pandemic dramatically accelerated both trends simultaneously, with home nesting behavior boosting candle sales and the shift away from in-store shopping inflating package volumes.
E-commerce is a tide that lifts all shipping metrics and all shippable goods simultaneously. The correlation is real; the causation is Amazon.
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Want to learn more about why correlations like “USPS package volume” vs “US candle market retail sales” don't prove causation? Read our guide to statistical thinking.
