在現今關於公司現金決策的文獻中，多數文獻以預防性動機 (precautionary motive) 或是代理問題動機 (agency motive) 來解釋公司為何要存錢，但至今對於公司存錢的動機仍未有一致的定論。在本篇文章中，我們用籌資不易公司 (financially constrained firm) 在2000年網路泡沫以及2008年金融海嘯的表現來證明現金的預防性價值。我們發現事先有存錢的公司在上述事件期間仍能維持其原有的投資支出，反之事先沒存錢的公司在上述期間會擁有較低的股票報酬以及較高的違約風險。此外，本研究也發現曾在2000年網路泡沫期間遭遇資金問題的公司比較容易在2000年後開始存錢，這些預先存錢的公司在2008年金融海嘯來臨時也有相對較小的違約風險，顯示了公司在現金管理方面的學習行為及其好處。綜上所述，本文以外生事件突顯了現金的預防性價值，證明公司的未雨綢繆確實有用。 / This article examines the role of pre-saved cash in helping financially constrained firms during the 2000 dot-com crash and the 2008 financial crisis, both of which were exogenous shocks to industrial firms. The results show that constrained firms tended to increase capital investments during these severe economic downturns if they had pre-saved more cash. Constrained firms instead exhibited lower excess returns and incurred higher likelihoods of financial distress during the severe downturns if they had saved less cash prior to the events. Firms that experienced the 2000 dot-com crash and saved cash thereafter were less likely to default during the 2008 financial crisis, indicating the existence and benefit of learning effects. This study supports a precautionary motive for cash savings, showing that pre-saved cash helps financially constrained firms fund investment and reduces the likelihood of financial distress during severe market downturns. It demonstrates that saving for a rainy day really is valuable.