Underlying Index Performance: 00666R.TW tracks a specific index; the price largely mirrors that index's movements. Strong index performance leads to higher ETF prices.

Supply and Demand: Increased demand for 00666R.TW, often reflecting positive investor sentiment, drives the price up. Conversely, increased selling pressure pushes the price down.

Interest Rates: Rising interest rates can make bonds (if the ETF holds them) less attractive, potentially lowering the ETF price. Rate cuts can have the opposite effect.

Foreign Exchange Rates: Since the ETF invests in foreign assets, currency fluctuations between the New Taiwan dollar and the currencies of those assets impact the ETF's price.

Market Sentiment: General market optimism or pessimism can influence ETF prices, even if the underlying index remains relatively stable. Negative sentiment can trigger sell-offs.

Dividend Distributions: When the ETF distributes dividends, the price typically decreases by a corresponding amount, reflecting the value returned to shareholders.

Expense Ratio: Higher expense ratios charged by the ETF provider can, over time, slightly dampen returns compared to similar ETFs with lower fees.

Tracking Error: Deviations between the ETF's performance and its target index's performance can affect investor confidence and, consequently, the ETF's price.