Traditional looms then were stopped every few minutes in order to replace the empty weft pirns or cop in the shuttle and this limited the number of looms, a weaver could operate to about four. James Northrop, an English man who emigrated to America and worked for the Draper Corporation, completed an automatic weft transfer system which replaced the weft pirn in the shuttle without slowing or stopping the loom in 1889. This mechanism enabled the weaver to tend 16 looms. The Northrop Automatic looms quickly came to use in America, so that by 1930, 90% of the American looms were automatic compared with only 5% in Britain. Similar developments took place elsewhere also, Ruti, a major loom maker of Switzerland manufactured automatic bobbin changing Northrop loom in 1898. In Japan also, Toyoda, Sakamoto, Tsudakoma, etc also developed shuttle looms with automatic weft transfer. After World War II, more productivity and efficiency were essential to overcome increasing labour costs in Western countries. It was also realised that more productivity is the key to reducing manufacturing costs of the loom. All attempts were concentrated to studying various factors affecting speed of the loom and the loom with higher speed were made available.