The BBC News website has been speaking to Zimbabweans who have left the country in recent years about their reasons and the risks they took.
Last week the International Organisation for Migration launched a "Safe Journey" campaign in Zimbabwe, with help from some of the country's best-known musicians, to make would-be migrants aware of the dangers involved.
Mlamuli Nkomo, 26, is from Matabeleland South, and graduated from university in Harare before taking up a teaching post in Bulawayo. But he soon found the situation impossible, and left for Johannesburg.
Mlamuli sometimes does voluntary work, but employment is hard to find
I graduated in 2001 with a BA and became a teacher in Bulawayo. Teaching was very enjoyable and brought many challenges, but it soon became difficult.
Instead of a symbol of inspiration, teachers became an object of pity. When I was growing up, teachers were part of the middle class, but when I started working teachers were poor.
Things became politicised.
Sometimes teachers use newspapers as teaching aids - but you couldn't take an article from the [independent] Daily News because you'd be in trouble, and you couldn't take an article from the [state-owned] Chronicle because it would be lies.
If teachers demonstrate for a pay rise, they don't take it as a labour issue - they say we are against the government.
Because of fuel shortages, a lot of students from the townships couldn't make it to school. Because of commodity shortages, some parents encouraged their children to take days off school to queue for mieliemeal or sugar.
A worrying feature was the relationship between the teaching profession and the police. Police would come and lecture on "patriotism".
One day a student wrote on the blackboard "police should come to school to learn and not to intimidate students". I rubbed it off because if someone had seen it I could have got into trouble.
Once I was taken to the charge office. They said "how do you take charge of children with this mentality?"
Even soccer and politics became mixed. Once we were joking about the Highlanders, a successful club in Bulawayo. I said "if this club could be turned into a political party, they would beat Mugabe hands down".
I was given a severe warning by the police, and that was only because I had some friends in the police. If another teacher had said that, he would have been locked up.
With inflation, things became really difficult. I was privileged to live in the school hostel, so I didn't have transport costs, and I am not married so I didn't have dependents. But coming from an African setting one is expected to look after one's parents.
People were buying bread and milk on credit. Most colleagues had accounts at supermarkets, and the debts were then deducted from their salaries. When you buy a Coke on credit, then you know things are going down.
I left in March 2005. I won't lie and say I was being brutalised, but I felt I was in danger. I went to a National Constitutional Assembly [a coalition seeking law reform] meeting in Harare.
I heard from a policeman that my name and the names of other teachers had been mentioned at a Zanu-PF meeting as being a threat to Zanu-PF.
I left three weeks before the school term ended. I came here by taxi - I used my payslip as a visa, proving I was a government servant. I went to Pretoria to apply for asylum and managed to get my papers.
But that's just the initial phase. The next is applying for refugee status, and for that you need proof. They say they will call you for an interview, but I know people who have been here for five or six years and still have no interview.
Another problem is that the South African authorities don't understand why Zimbabweans come here.
Zimbabweans have always come to South Africa - with migrant workers there has always been a relationship, especially with southern Zimbabweans. Zimbabweans have always been part of South African life.
I have spent one and a half years in Soweto. Members of my family have always worked in South Africa, so I have family here. I am staying with my uncle who has never worked in Zimbabwe. For them, Zimbabwe is just another country.
I am not working, though I have applied countless times, generally for teaching jobs, facilitating HIV awareness programmes, in the area of research.
The Zimbabwe Crisis Coalition in Johannesburg provides a link with home
A relative took me to get a job at a restaurant, where they greeted me with a pile of fliers and told them to go and hand them out at the robots [traffic lights].
There was one of my former school students working there. She asked me "are you coming here to eat or to work?" - I didn't know what to say. She was now my senior.
I knew this was not my place, standing in the sun handing out fliers and not using my mental faculties.
It is better to do voluntary work.
I spend a lot of time here at Crisis [the Zimbabwe Crisis Coalition office in downtown Johannesburg] - it's the place to be if you want to hear news from home.
The South African government has failed to declare that there is a problem in Zimbabwe because as soon as they declare that, they have to accept refugees.
The denialism by the government of the Zimbabwe situation is causing people more problems.
We are already in Hell.
I think when Zimbabweans die, they must go straight to Heaven. You can't go from one hell to another.