Original sentence: China, South Korea, Hong Kong, Singapore, Thailand and Cuba are also below replacement levels, but this is not producing a fall in population yet in these countries, because their populations are relatively young due to strong growth in the recent past.Countries such as United Kingdom (the earliest nation universally recognised as reaching Stage Five), Germany, Italy, Spain, Portugal, Greece, and most notably Japan, whose populations are now reproducing well below their replacement levels, are not producing enough children to replace their parents' generation.Examples include Russia, Ukraine, Romania, and the Baltic States.However, many countries that now have sub-replacement fertility did not reach this stage gradually but rather suddenly as a result of economic crisis brought on by the post-communist transition in the late 1980s and the 1990s.The death rate can also increase due to "diseases of wealth", such as obesity or diabetes, leading to a gradual fall in population in addition to above aging.The original Demographic Transition model has just four stages; however, some theorists consider that a fifth stage is needed to represent countries that have undergone the economic transition from manufacturing based industries into service and information based industries called deindustrialization.The population of southern Europe is already falling, and Japan and some of western Europe will soon begin to fall without significant immigration.The population of these countries is falling due to fertility decline, emigration and, particularly in Russia, increased male mortality
Edited sentence: Development promotes fertility decline at low and medium HDI levels, but advanced HDI promotes a rebound in fertility.In an article in the August 2009 issue of Nature, Myrskyla, Kohler and Billari show that previously negative relationship between national wealth (as measured by the human development index) and birth rates has become J-shaped.In many countries with veryhigh levels of development (around 0.95) fertility rates are now approaching two children per woman - although there are are exceptions, notably Canada and Japan.Most European and many East Asian countries now have higher death rates than birth rates.The original Demographic Transition model has just four stages; however, some theorists consider that a fifth stage is needed to represent countries that have sub-replacement fertility.There may be a further stage of demographic development