**Core Concept**
The decline in percentage of alcohol usage in men and women over several years can be studied using a specific type of statistical analysis that measures changes in population trends over time. This concept is related to the field of epidemiology, which studies the distribution and determinants of health-related events, diseases, or health-related characteristics among populations.

**Why the Correct Answer is Right**
To study the decline in percentage of alcohol usage in men and women over several years, a time-series analysis is required. A time-series analysis involves the examination of data collected over a period of time, typically at regular intervals, to identify patterns and trends. In this case, a time-series analysis would involve collecting data on alcohol usage in men and women over several years and using statistical methods to identify any declines in percentage of alcohol usage. This type of analysis is particularly useful for understanding changes in population trends over time.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because cross-sectional studies examine a population at a single point in time, rather than over a period of time. While cross-sectional studies can provide valuable information about the prevalence of a particular health issue, they are not suitable for studying changes in population trends over time.
**Option B:** This option is incorrect because case-control studies involve comparing individuals with a particular health outcome (e.g., alcohol dependence) to individuals without that outcome. While case-control studies can provide valuable information about risk factors for a particular health outcome, they are not suitable for studying changes in population trends over time.
**Option C:** This option is incorrect because cohort studies involve following a group of individuals over a period of time to examine the development of a particular health outcome. While cohort studies can provide valuable information about the risk factors for a particular health outcome, they are not typically used to study changes in population trends over time.

**Clinical Pearl / High-Yield Fact**
When studying changes in population trends over time, it's essential to consider the potential impact of various factors, including changes in societal attitudes, economic conditions, and public health interventions.

**Correct Answer: D. Time-series analysis**