The post-war management faced many problems, including lack of records, which had almost all been destroyed by the Japanese and had to be reconstructed from the memories of serving and previous staff; shortages of coal for the engines necessitating their conversion to burning fuel oil; currency exchange rate difficulties due to devaluation of the Chinese currency requiring agreement with the Chinese authorities to use the Hong Kong dollar as the basis for all transactions; worn-out equipment; and staff shortages. At the same time, there was a huge demand for passenger and freight services as people who had fled to China during the war moved back to Hong Kong, and because huge volumes of goods needed to be carried into China to help in post-war relief efforts there. From an immediate post-war figure of around 600,000, the population of Hong Kong rose to nearly 2 million by the end of 1947, with the influx reaching a rate of about 100,000 per month during this period.