Final answer:
The question appears to relate to a demographic stage, likely regarding population levels from a sociological perspective. Without additional context, it is difficult to determine an exact figure for 'level 4'. Population pyramids and demographic transition models from sources like the U.S. Census Bureau can offer insights into such data.
Step-by-step explanation:
The question 'Roughly how many people live on level 4?' seems to be referring to demographic levels, which are often used to describe the stage of a population in terms of its growth and development. The question could be interpreted in the context of a population pyramid or demographic transition model, often discussed in social studies or human geography.
Given the information about Sweden's 1998 population being in Stage 4 of the demographic transition model, this stage is characterized by low birth rates and low death rates, leading to a stable or slowly growing population. If we relate this to the number of people living in such a population level in terms of U.S. demographics, the provided figure of 330 million corresponding to 2.5 people per household suggests we are discussing a large, developed nation's population dynamics. However, without a specific reference to 'level 4', it is challenging to give an exact number of people living at this level without additional context.
When dealing with population statistics, sources such as the U.S. Census Bureau or the International Data Base are valuable. If we take the example of Sweden, the population of a country in Stage 4 would typically range in the millions, seeing as it is indicative of developed or advanced societies. Using the provided poverty rate problem, in a nation of 300 million people, a significant portion of the population, sometimes millions, may live at different societal levels, including level 4. However, precise numbers would require specific details about what 'level 4' denotes in this context.