It is evident that the results of the market's behaviour in 2020 was something that nobody could or could not predict, which provides us with a great deal of uncertainty for this year.
However, 2021 begins with the resurgence of the Covid-19 with a new strain and a hard-hit economy.
Below, I present a brief analysis of the behaviour of oil, the dollar and bitcoin, in order to conclude a reflective analysis of what is coming in 2021.

Source
Petroleum
Likewise, between March and May, the lowest values of the barrel could be registered: March $ 33.73; April $26.85 and May 32.41.
This performance was maintained for the rest of 2020, with a small rise, reaching $ 43.98 in November and $50.26 in December, with a percentage variation of 14.28%.
There had not been a similar fall since December 1998, when the oil barrel reached $ 10.14.
Price Petroleum: January 1988-December 2020.Source
2021 is full of uncertainties, due to the appearance of the new Covid-19 strain, as well as the potential threat of further social isolation and paralysis of economic activities.
However, with the appearance of the vaccine and its application in some countries, it is hoped that the impact of this resurgence will not be as dramatic as it was in 2020 for oil and the world economy.
Price Petroleum: January-December 2020. Source
Dollar
The pandemic will therefore continue to be a risk to the world economy, but the economic recession and global uncertainty will be two factors that will work against the countries' monetary and financial balance.
The dollar's expectations for the period after the second half of 2021 are not very encouraging and point to the possibility of a culmination of the recent upward trend, which has been observed since July 2020, as shown in the graph below.
Price Dollar-Euro: January-December 2020. Source
Price Dollar-Euro: January-December 2020. Source
Bitcoin
In addition to the support given by large organisations during the second half of 2020, and now more recently the integration of Bitcoin into the Paypal platform and investments in Square in this crypt
Finally we can conclude, these three great assets of the world economy will have a particular and unpredictable behaviour for 2021, due to a key aspect that has all the fundamental pieces in the game, as it is the Covid-19, its control and management of governments and the reactivation of the world economy.