Is it because the Sony Walkman just had its 40th birthday? Is it because Peter Quill made personalised mixtapes with biro-written labels awesome again in Guardians of the Galaxy? Is it because you can now buy a Bluetooth portable cassette player? Is it because Sony has laid on a massive Wall of Walkmans exhibition in Tokyo? Is it just a natural offshoot of the vinyl revival?
We haven't the foggiest. What we do know is, cassette sales haven't been higher since 2004. According to company data from the home of the UK top 40, Official Charts, and figures from the British Phonographic Industry (BPI), some 36,000 cassettes have been sold in 2019.
Looking at 2019's biggest sellers, cassette sales clearly favour artists with a long-established fanbase, regardless of genre. Top of the Pops, though (sorry) is newcomer Billie Eilish with When We All Fall Asleep, Where Do We Go?, having shifted 4,000 copies – making it 2019's biggest seller so far.
Although cassette sales still only account for 0.2% of albums sold in the UK this year, sales are on a steady increase, apparently up 112% year-on-year so far.
Eilish's cassette was released in a variety of limited-edition colours: black, orange and UV green. The more acerbic wits among us point out that when 17-year-old Billie was born in 2001, cassette collections had been all but written off; chucked into the same bins as 8-tracks or given away at car-boot sales.
Number two in the best-selling cassette albums of 2019 is Catfish and the Bottlemen's The Balance, followed by Madonna's Madame X at number three, then Kylie Minogue's Step Back in Time – The Definitive in fourth spot and Lewis Capaldi's Divinely Uninspired to a Hellish Extent completing the top five.
If you've still got a few cassettes kicking around, now might be the time to start adding to your old collection. Just remember, you'll always need a pencil nearby, and you can't leave them out on your car's dash on a very sunny day...