Increased standards of living are a kind of background element, as they are more or less shared by the population. You seem to have gone backwards, and defined

Increased standards of living are a kind of background element, as they are more or less shared by the population. You seem to have gone backwards, and defined wealth as "only the things other people don't have", in which case of course it becomes a zero-sum. But that isn't what wealth is. The modern understanding of Wealth is the abundance of valuable resources or material possessions. [...] In this larger understanding of wealth, an individual, community, region or country that possesses an abundance of such possessions or resources to the benefit of the common good is known as wealthy. -- Wikipedia