The word “poor” is defined as “having few possessions” by many dictionaries. Merriam-Webster’s online dictionary (n.d.) explains it as “1a: lacking material possessions” and “2a: less than adequate”. Cambridge Dictionary (n.d.) defines it as “A1: having little money and/or few possessions”. I related these definitions to a larger scale and assumed that a poorer society is where people possess less, which then leads to less consumption or investment. In other words, a richer society is where people gain an increasing after-tax income which provides them with richer material well-being. Therefore, in this paper, I focused on the relationship between people’s disposable income and population decline to see if population decline causes the reduction of their money with one possible reason.

I searched the relationship between the population decline and the average monthly disposable working household income in Japan. Japan’s fertility rate has fallen to 1.43 in 2017 since 1975 when the number first fell under 2.0 according to The World Bank Group (2019). Also, its “population is in rapid decline” (Ingber, 2018). So, Japan was appropriate for this research. I used data established from Statistics Bureau of Japan (2019-a, 2019-b & 2019-c), a part of Ministry of Internal Affairs and Communications, which annually conducts national censuses.

I measured the relationship by comparing the absolute population and the absolute average of monthly workers’ household disposable income from 2003 to 2017. The income shows the amount which is already deducted by the non-consumption expenditure such as taxes. The population data of 2005, 2010, and 2015 were unavailable so they are remained blank. I found that both figures have fallen gradually, both showing negative trendlines (Figure 1). The use of absolute disposable income for comparison is acceptable in this case since Japanese Consumer Price Index is in increase over the years (Trading Economics, 2019). From this result, I can see that the income level and population decline are correlated; in other words, the society gets poorer as the number of people decreases.