In American English, the verb model becomes modeled and modeling. Outside North America, the preferred participles are modelled and modelling, with two l‘s. Canadians prefer the double-l forms, though the single-l forms appear about a third of the time. (In contrast, the double-l forms are almost nonexistent in 21st-century American writing, and the single-l forms are similarly rare outside North America.) These spelling preferences extend to modeler (U.S.) and modeller (outside the U.S.).
Modelled and modelling were standard in American English until the early 20th century. Many verbs ending in -el—travel, duel, and panel, for instance —went through a similar change around this time. Others, such as cancel and label, changed only within the last few decades, so the double-l forms remain somewhat common in American writing. Still others, especially verbs ending in -pel (repel, compel, etc.), still make double-l participles even in American English.
Modeled to look like railroad cars, Long Island’s vintage diners offer a nostalgic trip back to simpler times. [Newsday]
Dannielynn was only 5 months old when her mother who catapulted into the modeling world. [Us Magazine]
Princeton’s Sam Wang, another modeler, also called the election almost perfectly. [Washington Post]
Outside the U.S.
As a consequence, financial products are modelled to take account of the differences. [Independent Online]
Two Kiwi analysts are heading to the United States where they will battle it out for the title of financial modelling world champion. [New Zealand Herald]
The team’s computer modeller … has reconstructed the tsunami. [Economist]