The Wall Street Journal sought a powerful way to illustrate the tech boom and the explosion of capital flooding startups. The resulting interactive spurred a new investigative series called “Private Risk,” which examines the intersection of Wall Street and Silicon Valley. For the startup companies that populate Silicon Valley, the idea of raising $1 billion has long been hailed as a near-mythical achievement. The 2010 movie about Facebook Inc., “The Social Network,” hammered this notion into the mainstream American lexicon. But it has become clear that a $1 billion valuation for a startup is no longer unusual. In early 2015, our research found that more than 80 startup companies were valued at that amount and the list was growing as never before. Just a few years earlier, only a handful of companies had achieved this milestone. We needed a way to better track this boom and create a trusted resource for readers who may not have heard of these companies. Over time we hope to show the expansion and contraction of capital, perhaps a visual accounting of a boom and a bust. At the top of the interactive, we created a unique radial bar that displays the size of each company's valuation over time. Readers can move a slider underneath the chart between months, enabling the radial bar to contract or expand along with a sortable table below that includes written profiles of all the companies. These profiles are created by dozens of Journal reporters around the world, based on interviews with each company. The Billion Dollar Startup Club has become a dependable resource for readers and is often cited online and in internal reports by big firms such as Goldman Sachs. The interactive allows us to enhance our articles dealing with startups; related coverage is linked along the right rail of the interactive. The list now includes more than 125 companies, double the number we started with.