evidence: While the creation of the common travel area in 1923 allowed movement of peoples, over time the border would become a customs and security control that took on social, cultural and political significance. The decision by the then Irish Free State in the early 1930s to industrialise behind a tariff wall served to deepen the economic divide. [...] There have also been increases in tourism, investment and travel. Around 30,000 people cross the border daily for work purposes and approximately 177,000 lorries and 250,000 vans cross each month. Trade is now valued at around £3 billion a year. [...] For the 1.81m people in the North and the 4.78m people in the Republic, this cross-border trade is huge. Of particular importance is the agricultural processing industry with supply chains crossing the border several times before final production.