Final answer:
The time series data is 'The average cost of a house in the United States every year since 1820', as it provides data points across various times, allowing analysis of trends and patterns in the housing market.
Step-by-step explanation:
The time series data is a series of points of data in time order. It is typically used to track the characteristics of subject(s) over various points in time. In the context of the question provided, 'The average cost of a house in the United States every year since 1820' represents time series data. This data could be used to analyze trends, forecast future prices, or assess the impact of certain events on housing prices. It reflects how housing prices have changed continuously over a fixed period, making it possible to observe trends and patterns.
On the other hand, 'The height of each professional basketball player in the NBA at the start of the season' is not time series data. It is cross-sectional data because it involves multiple subjects at a single point in time.
The housing market often shows a cumulative average annual growth rate in housing prices, as depicted in the historical information provided. For example, the period from 1981 to 2000 showed a 5.1% average annual growth, whereas from 2003 to 2005, home prices surged more than 10% per year. Understanding these figures is essential for analyzing the sustainability and patterns within the housing market.