This map shows the total solar power capacity for each country. Interestingly enough, solar/photovoltaic energy only made up 1% of total energy production in the world in 2016. Since then it has been growing explosively at 33% per year.
More Countries Are Increasingly Generating Energy Via Solar
Photovoltaic cell costs are reducing as time goes on, production costs are decreasing. This is one factor. Add to the fact that in 1975 it was nearly $100 per Watt to produce, whereas in 2015 the price-per-watt was at mere $0.61, a decrease of over 99%.  It is less likely that people now tolerate the traditional methods of generating energy such as coal that cause global warming, as we become more aware of the alternative clean solutions, coverage is increasing globally.
Swanson’s Law & Photovoltaic Module Cost Reduction
The changes of solar panels can also be explained with Swanson’s law which states that the price of solar PV modules decreases by around 20% for every doubling in global solar capacity.  Taking this law into account, we can draw parallels to the computing industry which follows Moore’s law which states that the number of transistors on a dense integrated circuit board (think of your CPU) doubles every 2 years. Remember how much a laptop would cost back in 2007 compared to 2018. The production costs will decrease over time for PV solar manufacturers, which could lead to more coverage as more of the global population adopts them.
Global Solar Power Facts
- In 2015, China became the largest producer of solar power when they reached 100GW of cumulative install capacity 
- China is set to be the global leader in solar PV capacity over the next decade
- In Q4 of 2016 the cumulative PV capacity globally was at 302GW which constitued between 1.3-1.8% of global energy usage at the same 
- The European Photovoltaic Industry Association (EPIA) claims that installed worldwide capacity of solar panels will double, or maybe even triple to 500GW between 2016-2020
- The EPIA claims that by 2050 solar power will become the most largest source of electricity – this would require PV capacity to grow to around 4,600GW, of which more than 50% would be covered by China & India 
Top 20 Countries By Solar PV Capacity (MW)
 – https://cleantechnica.com/2016/02/12/is-this-the-best-solar-chart-yet/