What happened Shares of JinkoSolar Holding Co. (NYSE: JKS) jumped a whopping 127.4% in December, according to data provided by S&P Global Market Intelligence, as financial conditions rapidly improved. Shares were quite volatile throughout the year but ended with a surge after third-quarter results were announced. So what The overarching drive of JinkoSolar's stock was a rise in gross margin and ultimately profitability in 2019. Investors came into the year thinking it might be a down year after China cut subsidies and U.S. demand seemed tepid, but it turned out to be a strong year from the demand side. Final numbers aren't out yet, but one analysis expects that solar installations jumped 25% in 2019 to 125 gigawatts (GW). Image source: Getty Images. Growth is great for JinkoSolar, but what really helped the bottom line was a trend toward higher-value and higher-margin solar panels. Developers are now shifting toward mono-crystalline silicon solar panels, which are more expensive than their multi-crystalline competitors, but which produce more power as well. That shift helped third-quarter 2019 gross margin improve to 21.3% from 14.9% a year ago. JKS Revenue (TTM) data by YCharts. You can see that the result was a solidly profitable one last year for JinkoSolar. Now what Any short-term move by a solar stock like JinkoSolar should be taken with a grain of salt, but the long-term trends you see above are undeniable. Margins are improving, sales are rising, and net income is improving as well. 2019 was a great year for JinkoSolar stock, but with a $4 billion market cap, there may be upside in 2020 as well. 10 stocks we like better than JinkoSolar Holding CompanyWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and JinkoSolar Holding Company wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of December 1, 2019 Travis Hoium has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source