Corruption affects all countries, undermining democratic institutions, stunting economic development and contributing to governmental instability. It is the single greatest obstacle to economic and social developmental in the world.
Every year, $1tn (£640m) is paid in bribes, while an estimated $2.6tn is stolen annually through corruption. In developing countries, according to the United Nations Development Programme, funds lost to corruption are estimated at 10 times the amount of official development assistance.
Moreover, corruption leads to weak governance, which fuels organised criminal networks and promotes human trafficking, arms and migrant smuggling and other practices detrimental to human rights.
This year's theme for International Anti-Corruption Day, observed annually on 9 December, is "break the corruption chain" – a campaign fronted by the United Nations Development Programme and the United Nations Office on Drugs and Crime. It focuses on human rights violations, distorts markets, erodes quality of life and allows threats to human security to flourish.
IBTimes UK looks at the world's five most corrupt countries – and why the phenomenon is rife.
Conflict-torn Somalia faces one of the longest instances of state collapse in recent years, with rampant corruption in key sectors such as ports and airports, tax and custom collection, management of aid resources and immigration.
Corruption is further exacerbated by the absence of a functional central government, weak leadership structures and a lack of resources and administrative capacity – as well as a limited ability to pay public officials, according to Transparency International.
Piracy off the Somalian coast, which has posed a threat to international shipping since the second phase of the Somali Civil War in 2009, along with the Islamist militant group al-Shabaab, also contribute heavily to state corruption.
Corruption in North Korea is a widespread problem, so much so that "the political system is basically relying on corruption", according to a lead researcher for Transparency International. The regime, headed by Kim Jong-un, imposes strict rules against accessing foreign media and freedom of movement, while bribery is rife and most labour goes unpaid.
In February 2014, a UN special commission published a detailed, 400-word account based on first-hand testimonies that documents "unspeakable atrocities" committed in the country. The Human Rights Council compared regime brutality and human-rights violations in the state to those by South Africa during the apartheid and Nazi Germany.
North Korea's state media admitted widespread corruption in the country when laying out the accusations against Jang Sung-taek, after his execution in December 2013.
Sudan has endured decades of political turmoil and civil war and, as a result, faces many of the corruption and governance problems that affect conflict-ridden and resource-rich countries.
Fragile state institutions, weak systems of checks and balance and blurred distinctions between the state and ruling party has led to Sudan being one of the most corrupt countries in the world.
Since South Sudan was formed in 2011, corruption has permeated all sectors, from embezzlement of public funds to a system of entrenched political patronage in society.
There is also little evidence of the impact of corruption, as it is concealed by the country's economic and political instability, but corruption among police and security forces is known to allow abuses of political and civil rights.
In 2013, Afghanistan was ranked the most corrupt country in the world by Transparency International. Although it has not topped the list this year, a leading US watchdog warned corruption is still a major problem.
"Corruption is really the big issue, John Sopko, the special inspector general for Afghanistan reconstruction (SIGAR) told the Middle East Institute in May this year, as reported by the Washington Post. The problem was attributed to a lack of planning surrounding foreign aid.
One of the major corruption cases was the 2010 to 2013 Kabul Bank financial scandal, involving businessman Mahmoud Karzai and others close to President Hamid Karzai, who were allegedly spending the bank's $1bn on their lavish lifestyles – as well as lending money under the table to friends and family. As of October 2012, the government only recovered $180m of the $980m fraudulent loans.
When the world's youngest country was created in July 2011, celebrations marked what was deemed the independence of a people who had been locked in a decades-long civil war with Sudan. Freedom of speech, democracy and prosperity were to be central to South Sudan, after the authoritarianism inflicted by Khartoum.
But the optimism faded fast, amid widespread government repression, violence and abuses of human rights. In 2012, South Sudan's parliament suspended 75 senior officials accused of massive corruption, involving £2.6bn of stolen money.
The country has Africa's fifth-largest oil reserves, gold and plenty of arable land, but it is one of the poorest and least developed states in the world. Corruption in the region has been a problem since 2004, when South Sudan first gain control of oil revenue within its territory.