This year has definitely been the worst year for tech IPOs (Initial Public Offerings). As a matter of fact, experts said 2015 was the slowest year for tech IPOs since 2009. Fortunately, 2016 is looking better for IPOs.

Since the technology industry has been hardly hit this 2015, only 23 tech companies braved the market, a remarkable decline of 58 percent from last year. While many companies showed losses, others remained profitable. But here are 3 reasons why 2015 has not been a great year for tech IPOs.

1. Investors poured so much money into hot startups.

It's safe to say that there has been enthusiasm for tech companies. However, venture capitalists invested more into hot startups, pushing their valuations to billions. Additionally, several tech companies saw little reason to go public. Hence, they opted to stay private longer and raise more venture cash instead of enduring frigid winds of the public markets, Business Insider noted.

2. IPO market started with "gusto."

This year, the IPO market began with so much enthusiasm. Unfortunately, it nosedived in August and September, wiping out positive performance and driving abnormally high IPO discounts as well as bringing issuance to almost a stop by year-end, as per Renaissance Capital (via San Francisco Chronicle). Even if the broader stock market recovered from its late-summer collapse, IPOs did not.

3. Biotech progressed well.

This 2015, healthcare became the standout factor, particularly the biotech companies, which accounted for 46 percent of this year's IPOs compared to 37 percent last year and 9 percent in 2012.

"One reason for the (IPO) slowdown, we think, is that many companies would have to price below their last private round of financing," Renaissance's Kathleen Smith said. "It's a big disappointment to all the startup companies who always assumed the IPO was done at a higher price. 2015 is a wake-up call that that's not the case and the (IPO) window is not open at all times."

While 2015 is the year of many disappointments for tech IPOS, there were also some winners, even late in the year. One example is the Australian company Atlassian, which has a San Francisco headquarters that makes business-collaboration software. It went public on Dec. 9 at $21 per share, above its expected range. Today, it's growing fast and has good profit margins, with current trading at $29.35.

Other notable IPOs that fared well this year include Box, Etsy, Shopify, FitBit, Square and Match Group, Venture Beat listed. For a more comprehensive report about the worst and the best tech IPOs in 2015, you can check out Quartz.