Ever been tempted to buy two copies of a Lego set – one to build and another to hide in the loft? Buying sealed Lego sets in the hope that they’ll become more valuable has become a hobby in its own right. A widely cited academic study – Lego: The Toy of Smart Investors – examined unopened Lego sets sold between 1987 and 2015 and calculated an average annual return of at least 11% across its sample. That’s an impressive historical result, although it certainly doesn’t mean every Lego set rises by 11% each year or that modern releases will perform in the same way. Most Lego sets aren’t produced forever.