1.   Their works tended to be small-scale, mostly because they worked in cramped living spaces with scarce materials.

2.   Controls over foreign exchange, credits and scarce materials could hardly force anybody to expand.

3.   But Riddell said they could rise in price if they become more popular, because they are made from relatively scarce materials.

4.   When factories are working at top speed, production bottlenecks often occur and can lead to inflation as companies bid up the prices of scarce materials and skilled workers.