本研究探討基金購併決定的因素及其事後的結果，主要是從被併(主併者)與其家族之間的關係探討之。研究期間為1996年至2008年，共計2,334個被購併之股票型基金為樣本，並包括242個家族。本研究並未將被併或主併基金視為單一基金，而是從家族的角度來看。我們假設家族在基金購併中扮演三個角色，第一是消除無效率的基金；第二是將資產轉入家族中其它基金，以支助其它基金的成長；第三則是達成整體家族的成長及促進家族規模經濟。
我們發現被併的基金相對於併它的基金及它的家族規模較小，有較低的現金流量，有較高的風險、週轉率及費用率。此外，實證結果也顯示被併基金的績效在合併後相對於合併前有較佳的績效，但相對的，這些購併者併了別人的基金，大約要經過二年的期間才能恢復到它購併前的績效，主要原因是經理人接收了之前較差的基金。實證結果也顯示出這些購併者在購併後相對於它的家族是有較佳的績效。此外，費用率在購併後也隨之降低。
邏輯式迴歸亦顯示當家族的績效差，家族的資產流量較差，家族規模較小，家族週轉率較小，但是家族費用率較高，愈容易產生被併的基金。此外，較年輕及成立年數愈久的家族愈容易產生被併的基金。接著我們又看基金相對於家族的差異，探討在什麼情況下較容易產生被併的基金，我們發現基金相對於它的家族績效愈差、規模愈小及較老的基金愈容易被購併；另外基金相對於它的家族有較高的風險、週轉率及費用率也較容易被購併。
當家族有較多的投資標的且為較大的家族時，則較易產生主併的基金，此外，當家族有相同投資標的基金時，也較易產生主併者。
至於同家族與跨家族基金合併的差異，我們發現當家族有較多的投資標的時及較大的家族時，較容易採同家族合併。至於從基金相對於家族的觀點來看，我們主要的發現有三點，第一我們發現跨家族的合併，基金的績效並不是一個重要的因素，這與我們的假設一致，同家族合併主要是消除無效率的基金；第二，同家族的合併，更傾向於要消除高成本結構及較老的基金；第三，規模愈小的基金愈容易被同家族合併。
最後，我們測試當家族有基金被購併是否會增加家族的現金流量及達到家族的經濟規模？實證結顯示只有在購併後一年可以增加家族的現金流量，第二年後就無法增加家族的現金流量，當家族採取同家族合併亦較能為其家族籌措到更多新的資金。至於購併是否可促成家族的經濟規模，我們發現購併後第二年及第三年，家族的費用率有明顯的下降，但是若採取同家族合併，並不會導致家族費用率的下降。

This study investigates mutual fund mergers in order to understand the determinants and consequences of fund mergers and especially focuses on the roles of acquired (acquiring) funds with their family. Using a sample of 2,334 equity mutual fund mergers and 242 families over 1996 through 2008 period, instead of treating mutual funds as if they were stand alone entities, we view them as part of mutual fund families. The mergers in mutual fund dynamics play three roles. The first role is to eliminate inefficient funds. In the second role, mergers are used to support the growth of other funds in the family by moving assets to them. The third role is to exploit family economics of scale.
The results show that acquired funds tend to be significantly smaller, experience relatively lower asset flows, and have higher risk, turnover ratios and expense ratios than acquiring funds and its family. We find that acquired funds experience significant improvements in performance after a merger is completed. Acquiring fund shareholders experience a significant deterioration in post-merger performance in about two years. This may be due to the inability of the manager to liquidate poorly performing assets that were held by the merged fund prior to the merger. Results also show that acquiring funds tend to exhibit better performance relative to their families in the year after the merger. The expense ratios of the combined funds will decline following the merger.
Logistic regressions suggest that the likelihood of producing an acquired fund is inversely related to family performance, family flow, family size, and family turnover ratio, but positively related to the family expense ratio of the merged fund. Younger fund families and older families all exhibit a greater likelihood to participate in a merger. To examine the relationship between the merged fund and his family, we use adjusted fund characteristics to test the probability of producing a merged fund. We also find if a fund relative to its family is poor, small and older, it is more likely to be merged. High risk funds, high expense ratio funds and high turnover ratio funds also can increase the probability of a fund merger.
A higher numbers of objectives in the family and a larger family are more likely to find an acquiring fund. Furthermore, funds in a family having similar investment objectives in the period prior to the merger are more likely to produce an acquiring fund.
As to the differences of within- versus across-family mutual fund mergers, we find that families with a larger number of investment objectives are more likely to engage in a within-family merger. In addition, large families are more likely to find an acquiring portfolio for within-family mergers. To look at the relationship between a merged fund and its family, we find three differences. First, performance-merger likelihood relationship is insignificant for an across-family merger. This is consistent with our hypothesis that within-family mergers are most likely driven by the need to eliminate the poor performance funds within a fund family. Second, within a fund family, there seems to be a greater desire to eliminate funds with higher underlying cost structures as well as older funds. Third, smaller funds are more likely to be merged in within-family mutual fund mergers.
Finally, we test the effect of merged funds on family cash flows and family economics of scale. The results show that after a merger, the family experiences significant fund inflow after the merger is completed, but only during the subsequent year. If the merger takes within family mergers, this also can help a family attracts more new money. As to the impact of having a merged fund on family economic scale, we find the family also benefits from a reduction in its expense ratio after the second and third year post merger. However, if the merger takes within family mergers, this will not help its family reduce its expense ratio.

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