The frenetic era of billion-dollar start-up unicorns is slowing significantly, according to CB Insights. The first red flag was the decline in "megarounds," of $100 million or more, beginning in Q4 2015.

Unicorns are being dramatically impacted in terms of share price by renewed market volatility in 2018. An end to the era of ultra-low interest rates from the Federal Reserve will also weigh on these overvalued names. As interest rates continue to rise throughout 2018, that will accelerate the unicorn slowdown.

Expect to see more dead unicorns. Several high-profile billion-dollar start-ups missed their 2017 year-end revenue targets, including BuzzFeed, Vice Media and Credit Karma, according to the Wall Street Journal. That causes a rift between the start-ups and their results-driven investors of multiple share classes that makes it even harder to raise late-stage capital. The WSJ found that after the second year the returns of unprofitable companies gradually declined even further.

Most unicorn companies aren't producing billions of dollars of revenue. Several financial models project that up to 80 percent of unicorn companies are set to fail within two years. Uber, the highest-valued private technology company, has rapidly growing revenue but remains highly unprofitable. With revenue of $6.5 billion in 2016, it still registered a net loss of $2.8 billion.

The truth is, when a unicorn is overvalued, it doesn't take long for the market to discover this fact. Great odds for a VC batting .300, but not great for your average investor on Main Street and potentially in one or more mutual funds that have invested retirement assets in these companies.

If you intend to invest in a unicorn IPO anytime soon, think twice. And if you haven't taken a close look at your 401(k) or IRA retirement plan investments, check to see what those mutual funds have been dabbling in.

We are now officially in a tech bubble larger than March of 2000. The term unicorn in business parlance was created in 2013 by venture capitalist Aileen Lee. This mythical animal represented the statistical rarity of a start-up company valued at over $1 billion dollars. The term may not last much longer in the financial vernacular than many of the start-ups that were — wrongly — branded with it.

— By Keith Wright, Instructor of accounting and information services at the Villanova School of Business