Pre-1983
During the period post-independence and prior to Black July 1983, there was not much migration.
However, this changed as the government of Sri Lanka, which tended to be controlled by Sinhalese started introducing policies, such as the Sinhala Only Act, which curtailed opportunities Tamils in Sri Lanka.
Before 1956, Tamils were proportionately over-represented in the civil service because of their high achievement and perceived preferential treatment by the Colonial Rulers. Until 1956, this was their passport to government employment. As Cheran (2000: 110) argues, "he class dimension of the Sinhala Only Act must not be forgotten. The battle of the languages was in reality a battle for government jobs." Unemployment among Sinhala youth generated considerable political pressure for the government to act in a manner that ironically consolidated identity based on nation, despite the economic antecedents to such identity formation. Although the Sinhala Only Act was partially repealed in 1959, it did not stop Tamils leaving Sri Lanka searching for better employment opportunities.
Read more about this topic: Sri Lankan Tamil Diaspora