定期定額投資（Dollar Cost-Averaging，DCA，又稱為成本平均法）是在中國基金行業一種受歡迎的投資方式，超過三分之一的共同基金投資者採用這一方法。該投資方法起源於美國，由Vanguard Group於1987年首次提出，此後在中國得到廣泛應用。DCA允許投資者在固定的時間間隔內，以相同的金額定期購買投資工具（如股票、基金等）。通過定期投資，投資者能夠分散市場波動風險，因為他們購買的份額價格可能在不同的市場狀況下減少波動。DCA契合長期投資的理念，有助於長期積累資產，並降低因市場波動而導致的短期損失。運用DCA的投資者無需過度關注市場波動，因為投資金額是固定的，有助於維持情緒穩定，避免決策受短期市場波動影響。隨著美國共同基金行業的繁榮，基金從業人員在DCA的基礎上開發出增強型定期定額投資法（Enhanced Dollar Cost-Averaging，EDCA，又稱增強型成本平均法）。EDCA通過在市場表現較差時增加投資金額，表現較好時減少投資金額，以更好地把握市場機會。這種策略旨在不同市場情況下優化投資表現，EDCA本質上也是一種逆週期投資策略。EDCA的動態性質使其更適應變化的市場條件，有助於更主動地控制投資風險，降低投資組合的波動性。

但是，金融學界對DCA和EDCA的有效性的尚未達成一致。首先，DCA假設投資者無法在市場的高點和低點做出正確的擇時決策，在市場有效（Market Efficiency）的情況下，DCA採取定時投資的方式可以彌補投資者在判斷上的不足。但是近來越來越多的證據挑戰了有效市場假說，當市場異象可以預測未來收益的情況下，DCA的有效性應另當別論。在機會成本方面，一些學者認為一次性買入可能在市場低點獲得更低的價格，而DCA投資可能會錯過這些機會。對於EDCA，爭議主要集中在投資者是否能夠準確預測市場表現，以便有效地調整投資金額。市場的複雜性使得準確的短期預測變得困難，一些學者擔心EDCA可能導致過度交易，頻繁地調整投資金額可能增加交易成本，並對投資者的綜合回報產生負面影響。EDCA的有效性可能在不同的市場環境下有所不同。在極端市場波動的情況下，EDCA的動態調整可能會面臨更大的風險。

本研究採取使用2002至2022年中國公募基金資料，運用DCA和EDCA策略對中國公募基金進行模擬投資，來證實DCA和EDCA策略運用在中國基金市場的有效性。本研究的EDCA策略遵循業內的“逆週期”思想，即資產價格下跌時多買入，資產價格上漲時少買入。本研究還創新性的提出了DEDCA（Dynamics EDCA）策略，即在持倉時加入了融資工具，EDCA的策略判斷的買入額度限制在了最大現金持有量，但是DEDCA可以以市場利率貸款現金後買入資產;同理，在持有多餘現金時也可以獲取市場利率產生的利息。為了體現長期投資的有效性，本研究為DCA、EDCA和DEDCA策略創建了一年、三年和五年持有期。為了研究策略整體表現和基金個體在策略下的表現，本研究引入總帳戶和子帳戶的概念。最後，本文還研究了基金特性，例如基金類型、基金投資風格、管理費率等，對DCA、EDCA和DEDCA以及三種持有期所產生的收益和風險的影響。研究發現，EDCA、DEDCA策略從多個策略終值變數上擊敗了DCA策略，長期投資策略有助於控制風險，在長期投資策略下，基金投資風格對策略的收益和風險沒有產生影響。

成本平均法十分符合中國基金市場的特性，中國基金行業提供了多樣化的基金產品，包括股票基金、債券基金、混合基金等，並且中國股市和基金市場的波動性較高，投資者很難準確預測市場的漲跌。本研究的創新策略有望在中國的基金行業施展拳腳，並大放光彩。

Dollar Cost-Averaging (DCA) is a popular investment method in China's fund industry, used by more than one-third of mutual fund investors. Originating in the U.S. and first proposed by the Vanguard Group in 1987, DCA allows investors to purchase investment instruments (e.g., stocks, funds, etc.) at regular intervals for the same amount of money. By investing at regular intervals, investors are able to diversify the risk of market volatility, as the price of the shares they purchase may fluctuate in different market conditions. DCA fits the concept of long-term investment, helping to build assets over time and reduce short-term losses due to market volatility. Investors who utilize DCA do not need to be overly concerned about market fluctuations because the amount invested is fixed, helping to maintain emotional stability and prevent decisions from being influenced by short-term market fluctuations. With the boom of the mutual fund industry in the U.S., fund practitioners developed Enhanced Dollar Cost-Averaging (EDCA) based on DCA. EDCA helps investors better capitalize on market opportunities by increasing the amount of money invested when the market performs poorly and decreasing the amount of money invested when the market performs well. market opportunities. This strategy is designed to optimize investment performance under different market conditions, and EDCA is also essentially a countercyclical investment strategy. The dynamic nature of EDCA makes it more adaptable to changing market conditions, helping to control investment risk more proactively and reduce portfolio volatility.

However, the financial community has not yet agreed on the effectiveness of DCA and EDCA. First, DCA assumes that investors are unable to make correct timing decisions at high and low points in the market, and under Market Efficiency, DCA can compensate for investors' deficiencies in judgment by adopting a timed investment approach. However, more and more evidence has recently challenged the efficient market hypothesis, and when market anomalies can predict future returns, the effectiveness of DCA should be treated differently. In terms of opportunity costs, some scholars have argued that a one-time buy may result in lower prices at market lows, and that DCA investments may miss these opportunities. In the case of EDCA, the controversy centers on the ability of investors to accurately predict market performance in order to effectively adjust the amount invested. The complexity of the market makes accurate short-term forecasting difficult, and some scholars are concerned that EDCA may lead to over-trading, and that frequent adjustments to the amount invested may increase transaction costs and negatively affect investors' overall returns. The effectiveness of EDCA may vary in different market environments. Dynamic adjustment of EDCA may be riskier under extreme market volatility.

This study takes a simulated investment in Chinese public funds using DCA and EDCA strategies using Chinese public fund data from 2002 to 2022 to confirm the effectiveness of the use of DCA and EDCA strategies in the Chinese fund market. This study innovatively changes the core idea of EDCA from the original "counter-cyclical" investment strategy to a "pro-cyclical" investment strategy, i.e., sell when the previous position is losing and buy when the previous position is gaining. This change makes EDCA consistent with the Momentum Factor strategy. This study also innovatively proposes the DEDCA (Dynamics EDCA) strategy, that is, when the position is added to the financing tool, EDCA's strategy judgment of the purchase amount is limited to the maximum cash holdings, but DEDCA can be at the market rate of interest rate loan cash and then buy the asset; similarly, when holding excess cash can also be obtained when the interest rate generated by the market rate. In order to demonstrate the effectiveness of long-term investing, this study creates one-, three-, and five-year holding periods for the DCA, EDCA, and DEDCA strategies. Finally, this paper also examines the impact of fund characteristics, such as fund type, fund investment style, and management fee rates, on the returns and risks generated by DCA, EDCA, and DEDCA and the three holding periods. It is found that the EDCA and DEDCA strategies beat the DCA strategy in terms of a number of strategy end-value variables, that the long-term investment strategy helps to control risk, and that the fund investment style has no effect on the return and risk of the strategy under the long-term investment strategy.

The fixed-term strategy fits well with the characteristics of China's fund market. China's fund industry offers a diverse range of fund products, including stock funds, bond funds, and hybrid funds, etc. Moreover, the volatility of China's stock market and fund market is high, and it is difficult for investors to accurately predict the ups and downs of the market. The innovative strategies in this study are expected to play a role and shine in China's fund industry.