What stock will go up the most in 2020? We'd all like to know that one. And it's a question that's a lot easier to ask than to answer. Let's start by looking at the top 10 stocks of 2019 for clues. The No. 1 stock of 2019, Axsome Therapeutics, had a staggering 3,578% return for the year.

But would you be able to hold on to that horse for the entire year? That might be the most important rule for seeking profits in 2020: Find a winner and hold on to it.

Here are some predictions about what the top stock in 2020 will look like.

An upward arrow next to a large 3D 2020.

Image source: Getty Images.

The No. 1 stock of 2020 will start off the year as a small company

Last year's top 10 list was filled with small caps and former micro caps. Of course, it's possible that a large cap or two will sneak into the top 10 list this year, but it's unlikely. And it's highly unlikely that the No. 1 stock will start off the year as a large cap.

It's true that Apple's stock nearly doubled last year. That's an amazing accomplishment for a huge company like Apple. And yet Apple didn't make the list of top stocks last year. The No. 10 stock, ArQule, was a seven-bagger for the year. Investors in that small cap did seven times better than Apple investors.

It's incredibly difficult for a large cap to double or triple in size in a year. It happens, but it's rare. And even that rare event is small potatoes compared to the massive returns that the top stock of the year makes. If we are searching for the strongest stock in 2020, the best profit opportunity is in small caps, not large caps. 

The No. 1 stock of 2020 will be surprising

Investors value certainty and predictability. One of the reasons software-as-a-service stocks are so popular is that these companies often enjoy recurring subscription revenue streams. Or, the company enjoys strong network effects that make the business increase in value as the network gets bigger. This predictability is why stocks like Shopify and The Trade Desk have been fantastic investments that double in value almost every year.

The top 10 stocks from last year aren't like that. A stock that goes up in value 1,066% in a year is a different kind of animal. Constellation Pharmaceuticals ran up that much last year because it had surprisingly positive results from a clinical trial. That stock jump reflects the market's reaction to a company that is moving from unpredictability to predictability. That's why the top 10 list is filled with so many biotech companies. There's a huge amount of unpredictability (and risk) in the biotech sector. When a company's scientific assumptions become validated in clinical trials, its valuation can skyrocket. 

What this means is that it's inherently risky trying to find and invest in what might become the year's top stock. You might have more success investing in a company with more certain growth rates, like Shopify or The Trade Desk. If you're chasing after the No. 1 stock for 2020, it will probably be a biotech or another company that makes a huge breakthrough.

The best stock of 2020 will surprise people. It will be a company with business prospects that are in doubt at first. And the business will be making a move from unpredictability to more certainty -- while the market becomes more and more bullish as a result.      

Two stocks that might pull it off

My first candidate is Virgin Galactic (NYSE:SPCE). The stock has already almost tripled in value in 2020. It went up 30% on Tuesday, and then came crashing down in the same day. The company started off the year as a small cap, and it's up to a $6.5 billion valuation in less than two months.   

Virgin Galactic's business model is bringing private space flights to the world. The company doesn't have any earnings yet, or even revenue, so the market's reaction to the company is both highly exuberant and highly negative (29% of its shares are sold short). Its business fundamentals are largely unknowable right now.

This will change later this year, as the company starts offering seats to the public, maybe as early as June, on its space flights. This is a stock that is moving from a high degree of uncertainty in its business to a more definitive business model. We'll start to have actual numbers from this company later this year. In the meantime, we can dream about how large this company might get. (Would you be interested in checking into a space hotel?) 

My second suggestion for the No. 1 stock of 2020 is Novavax (NASDAQ:NVAX). If the coronavirus becomes worse than we imagine, this stock market could suffer this year. But Novavax and other vaccine biotechs will certainly thrive. Novavax is a great defensive stock for those days when the market is pessimistic about this threat.

While the scare from COVID-19 has sent the stock up 88% this year, that's not the main reason to invest in Novavax. The company has a flu vaccine that has been walloping the market-leading vaccines in clinical trials. While the flu is more predictable than the coronavirus, its death totals are far higher than the coronavirus. Therefore, a flu vaccine that is superior to existing vaccines is very big news. 

Novavax expects to report its phase 3 results for its vaccine, NanoFlu, sometime this quarter. Positive news should send the stock soaring, in part because the market is so negative on the stock. Novavax is a tiny company, with a market cap of $254 million. And flu prevention is a $5 billion market opportunity. 

These two stocks are highly risky, and not for the faint of heart. It's hard to predict the top stock of 2020 since by its very nature, the top stock of the year will surprise the heck out of people. But both of these stocks have a good chance of making shocking returns this year.