????今年早些時候，我曾寫過一篇文章，提到了今年第一季度蕭條的科技公司IPO市場（四家公司募得2.21億美元），預示著2013年將是科技公司上市非常慘淡的一年。結果證明我錯了。其他人認為，對經濟的擔憂只是短時間內抑制了尋求上市的公司，今年下半年，IPO市場將收獲大豐收，實情確實如此。

????據復興資本（Renaissance Capital）統計，美國今年共有165家公司上市，比去年同期增加了45%。2013年還剩11周，至少從2007年以來，今年將是IPO市場最繁忙的一年。2007年共有213家公司上市。

????這些IPO中，約五分之一是科技公司——大多數都是基于軟件的商業模式，首次上市交易時的市值低于30億美元。而且，這些公司沒有一家像Twitter或規模龐大的Facebook、團購網站Groupon或社交游戲Zynga等公司一樣，屬于家喻戶曉的品牌。但凡知名度較高的股票都出現了增長——尤其是在各自移動業務的推動下——這也吸引了投資者對許多新上市科技公司的興趣。

????2013年的IPO主要由中小型公司組成。其中最大的公司所募得的資金并不突出。數據虛擬化公司Tableau Software在五月份募得2.54億美元。面向小企業的IT產品零售商CDW在六月份募得3.95億美元。網絡安全公司FireEye在上個月募得3.04億美元。

????相比之下，其他行業規模最大的IPO成績更加出色，比如從輝瑞制藥（Pfizer）拆分的碩騰（Zoetis）以及能源公司Antero Resources分別募得22億美元和16億美元。而募得160億美元的Facebook，規模之大在美國IPO歷史上排在第三位。

????Tabeau的上市似乎是今年IPO市場的關鍵轉折點。它最初申請發行720萬股，定價23美元至26美元之間，最終共發行了820萬股，每股價格為31美元。之后，這家公司的股票在五個月內上漲了115%。在Tableau之前，據復興資本統計，2013年共有七家科技公司上市。而這七家公司的交易價格均低于發行價，其中收入管理軟件公司Model N的交易價格比發行價下跌了39%。在Tableau上市之前，市場上唯一一家表現不錯的科技公司是云軟件公司Rally Software，自上市以來股價上漲了108%。

????在Tabelau之后，共有22家科技公司上市。除三家公司之外，其他公司股票均出現上漲。其中有四家公司的股價翻了一番以上，它們分別是：電子商務平臺暢路銷（ChannelAdvisor ）、項目管理軟件制造商Textura、廣告網絡Rocketfuel 和FireEye。

????這些公司之所以能有如此搶眼的上市表現，原因各有不同。其中，Tableau表明，今年前半年深受經濟不確定性的困擾，在這樣的狀況下，中型科技公司更受市場歡迎。Tableau公司是一家財務健全的增長型公司。還有一個原因是，Facebook和其他上市網絡公司報告了第二季度的收入，表明軟件與互聯網股票進入了移動驅動增長時期。

????另外一個原因是，歷史上，科技公司IPO會有一個蜜月期，這些公司的股票會上漲一段時間，幾周之后會緩慢下跌（自八月初以來，今年30家進行IPO的科技公司共有12家進行了初次上市交易）。例如，基于云的企業軟件公司Benefitfocus在上個月上市，每股股價為26.50美元，上市后第一周便上漲到55.87美元，上周跌至37.32美元。

????Earlier this year, I wrote that the sluggish tech IPO market in the first quarter of the year (four companies raising $221 million) presaged a bleak year for tech offerings in 2013. Boy, was I wrong about that. Others argued that economic concerns were temporarily holding back IPO candidates and that a bumper crop of them would emerge in the second half of the year, and this is indeed what has happened.

????According to Renaissance Capital, 165 companies have gone public on U.S. markets, an increase of 45% over the same period in 2012. We still have 11 weeks to go in 2013, and the year is shaping up to be the busiest for IPOs since at least 2007, when 213 companies went public.

????Nearly a fifth of those IPOs are tech companies -- most with software-based business models and all debuting with valuations below $3 billion. None of them are exactly household names like the upcoming Twitter IPO or past giants like Facebook (FB), Groupon (GRPN), or Zynga (ZNGA). But those better-known stocks are showing growth -- especially from their mobile business -- that are drawing interest into many of the new tech listings.

????The IPO class of 2013 is largely comprised of small or mid-sized companies. The biggest among them raised relatively modest amounts. Tableau Software (DATA), a data-visualization software company, raised $254 million in May. CDW (CDW), a reseller of IT products to small businesses, raised $395 million in June. And FireEye (FEYE), a network-security company, raised $304 million last month.

????Compare those to some of the biggest IPOs of the year in other industries, like Pfizer (PFE) spinoff Zoetis (ZTS) or energy company Antero Resources (AR), which raised $2.2 billion or $1.6 billion, respectively. Or Facebook's $16 billion in proceeds, the third-largest of any U.S. IPO.

????The debut of Tableau seems to mark a key turning point for IPOs this year. Tableau originally filed to sell 7.2 million shares between $23 and $26 and ended up offering 8.2 million shares at $31 a share. The stock has since risen 115% over the past five months.

????Before Tableau, according to Renaissance, seven tech companies had ventured out into the public market in 2013. All of them are trading below their offering price, as much as 39% down in the case of revenue-management software company Model N (MODN). The only pre-Tableau IPO to perform well in the market is Rally Software (RALY), a cloud software company that has seen it stock rise 108% since its offering.

????Since Tableau, 22 tech companies have gone public. Of those, all but three have seen their stock prices rise. Another four have seen their stock prices more than double: ecommerce platform ChannelAdvisor (ECOM), project management software maker Textura (TXTR), ad-network Rocketfuel and FireEye.

????There are a few reasons for that overall strong aftermarket performance. One is that Tableau, a financially healthy and growing company, showed that a mid-sized tech deal could receive a warm welcome amid the economic uncertainty that plagued the first half of the year. The other is that Facebook and other listed web companies reporting second-quarter earnings showed that software and Internet shares are entering a period of mobile-driven growth.

????Another reason may be that tech IPOs have historically enjoyed a honeymoon period when their stocks rise for several weeks before sinking down slowly (12 of the 30 tech IPOs this year have debuted since early August). For example, Benefitfocus (BNFT), a cloud-based enterprise software company, went public at $26.50 a share last month, then rose as high as $55.87 a share in its first week of trading before falling as low as $37.32 last week.