Historically, Scottish beers tend to be darker, sweeter and less heavily hopped than English and Welsh ales: a cold climate demands warming beers. But many of the new craft breweries produce beers lighter in colour and with generous hop rates. The traditional, classic styles are Light, low in strength and so-called even when dark in colour, also known as 60/-, Heavy or 70/-, Export or 80/- and a strong Wee Heavy, similar to a barley wine, and also labelled 90/-. In the 19th century, beers were invoiced according to strength, using the now defunct currency of the shilling.