“In Vietnam the last 10 years, we developed very rapidly because of low energy prices,” said Phu, who works at Fulbright University Vietnam. Postwar economic improvements have brought Vietnam a long way, but some are pausing now to reflect on the tradeoffs made in that time. Gross domestic product expands 6 to 7 percent every year. Meanwhile, though, the frequency of days when Ho Chi Minh City’s air is considered unhealthy for sensitive groups has doubled compared to two years ago.