The latest generation of Silicon Valley startup is now sprinting to the public markets, increasing the hopes of large and small investors eager to invest in these high-profile, fast-growing companies.
But the 2019 class is far different from its predecessors. These companies, including gig economy, darlings such as Uber and Lyft, are generally older and larger, driven for many years by billions of dollars of private money that has transformed the startup world.
The company's further maturity can slow down wild swings – both big gains and big losses – for new investors.
"Individual investors come in late," said Jason DeSena Trennert managing partner of Strategas Research Partners, a market and a financial analysis firm. "They're going to be the last investors in, and that's the concern."
The change reflects a major shift in the way American entrepreneurs make money to build their companies. Instead of quickly turning to public markets and the control that comes with which Amazon and Google did, they are building big businesses in the back of private money for many years and with fewer financial information requirements.  Uber, the giant equestrian company, has increased more than $ 20 billion over the last decade. Lift, the smaller competitor, as its price I.P.O. Late Thursday, at $ 72 per share, and expected to start trading on Nasdaq Friday, $ 4.9 billion rose in seven years.
Many startups in previous waves – back to the dot-com boom in the late 1990s, when Amazon was listed on Nasdaq – went public just a few years after they were founded. Some, like Pets.com, had small amounts of income and now exist only in Silicon Valley lore.
A combination of political changes and large new technology industries has changed the equation for start-up for more than a decade.
Funds and hedge funds – the typical investors in a startup are I.P.O. – began buying bets in large private companies as a way to build bigger bets before the new companies went public. Other major investors joined, including major sovereign mutual funds and the unmatched SoftBank Vision Fund, which create an even warmer market.
Venture capital investments in US-based companies grew to $ 99.5 billion by 2018, the highest level since 2000, according to CB Insights, a start-up company.
These investments have made valuations of startup at unusual heights. There are now at least 333 so-called unicorns, companies valued at $ 1 billion or more, according to CB Insights. In 2014, it was around 80.
Lyft has a private valuation of over $ 11 billion. It also does Pinterest, another company about to go public. It is about the market value that public investors place on the dealer Kohl and the electronic trading company E-Trade Financial.
Uber, the largest of the private companies expected to stock market shares this year, has a private market value of over $ 70 billion. In public markets, it is about as large as corporate giants such as Goldman Sachs and CVS Health.
Matt Murphy, a partner at Menlo Ventures, a leading venture capital firm, said that higher valuations and larger investments correlate with greater opportunities created by smartphones and cloud computing.
"The size of the audience that can be reached and revenue generation per user has grown," he said. "Their growth potential is much higher than previously expected."
Some industrial groups and investors who urge fewer regulations say that the weight of private markets is an outgrowth of the Sarbanes-Oxley Act, the federal law in 2002 tightened accounting rules for public companies according to the accounting scandals in the early 2000s.
In addition to disclosing disclosure requirements and other changes, law requires top executives to verify the accuracy of company accounts. Some say that the higher costs of guaranteeing compliance can prevent smaller companies from going public.
Private companies, like comparison, can operate with far less disclosure. They have no obligation to submit quarterly earnings updates or audited financial statements to the Securities and Exchange Commission. Nor are they forced to distribute business development updates to the public.
Others say the decline in public offerings began before Sarbanes-Oxley passed. They attribute the change to a wave of federal deregulation, making it easier to raise money and sell companies privately. Easier handling of antitrust is subject to a boom in mergers and acquisitions, allowing smaller businesses to sell to larger businesses rather than go public.
Whatever the driver, the net result has been a clear decrease in the number of public companies in the United States. The number of listed companies has fallen by 52 percent since 1997, to just over 3,600 in 2016, according to a National Bureau of Economic Research Working Document published last year.
This long-term shrinkage of publicly available stocks is one reason why some analysts expect Uber, Lyft and other prominent startups to receive a warm response from the institutional investors who usually buy new shares, even though the potential upside could be less.
"There is one element, I believe, of the demanded demand here," David Ethridge as a public offer advisor to the consulting firm PwC. "I think people will get a feeling that I really don't want to miss."
Investors have some reason to be skeptical about paying top dollar for newly developed public companies. In fact, over the past two years, the value of companies completing public offerings has fallen by an average of 8 percent, according to a recent research report from Goldman Sachs analysts.
During the same period, the share index for S & P 500 was around 12 per cent.