Which measurement of an investment's performance reflects its growth over time?

The measurement of an investment's performance that reflects its growth over time is appreciation. Appreciation refers to the increase in the value of an asset over time, which can happen due to various factors, including demand, scarcity, and improvements in associated economic conditions. When an investment appreciates, it signifies that its worth has risen from the initial amount invested, showcasing growth and the potential for profit when selling the asset.

Other concepts mentioned in the options, such as depreciation, market volatility, and equity, pertain to different aspects of financial performance. Depreciation refers to the decrease in an asset's value due to factors like wear and tear, not growth. Market volatility describes the degree of variation in a trading price series over time, indicating uncertainty rather than growth. Equity refers to ownership interest in an asset or company, which may not directly indicate growth itself without considering either appreciation or depreciation. Thus, appreciation specifically highlights the increase in value indicative of investment growth over time.