Vietnamese are handily finding jobs as the Southeast Asian country's economy expands on export manufacturing. Exporters hire workers. Prosperity of factories enables the launch of local suppliers and companies that do back-end services. The supporting firms create more jobs. The whole cycle increases the spending power of average citizens. By 2020 about one-third of the population will be middle class or higher, the Boston Consulting Group estimates. That means income of at least $714 per month.