Bulgaria's second largest city Plovdiv is an example of the country's thriving outsourcing industry, accounting for almost 4 per cent of GDP, according to the Bulgarian Outsourcing Association (BOA). Bulgaria is the world's ninth "most preferred" outsourcing destination in consultancy A T Kearney's 2014 Global Services Location Index, The Financial Times reports.

Fluency in languages and traditions in software development and programming are a draw, while macroeconomic stability and a currency pegged to the euro add to the country's appeal. Outsourcing employees' wages are low compared with western Europe, but allow a better quality of life than most sectors.

Investors have been attracted to the Plovdiv area in part by the Trakia Economic Zone (TEZ), a public-private partnership comprising six industrial zones clustered in and around the city. Companies are enticed by comprehensive infrastructure and fast-track procedures. TEZ is Bulgaria's first such area to receive focused state support, which allows even small municipalities to apply for project funding from the national budget or EU programmes.

Investment into TEZ projects has topped Ђ1bn since its zones started to grow in the 1990s, with another Ђ800m expected in the next 10 years.

"We're conservative in these estimates, the interest is steadily growing," says Plamen Panchev, TEZ managing director and chairman of construction group Sienit Holding, which played an important role in creating the TEZ.

More than 100 investors, most from Europe, have been drawn by business-friendly legislation, low labour costs and the 10 per cent flat tax that Bulgaria offers foreign companies. Among them are ABB, the Switzerland-headquartered power and automation group, and German supermarket group Kaufland.