The cryptocurrency market is the complex of all existing cryptocurrencies, the infrastructure and services that sustain their trade, and the community of people interested in buying and selling them.  Both the exchange rate of the cryptocurrencies and their market caps have historically been volatile because cryptocurrency is subject to price speculation.
From 2013 to 2017 the cryptocurrency market showed a steady growth. A 2017 study by researchers at City University London that analyzed the behavior of 1,469 cryptocurrencies between April 2013 and June 2017 concluded that, during this period of time, the cryptocurrency market was characterized by the continuous appearence and dissapearence of coins, an exponentially increasing market capitalization, and a few ever-stable traits, like the number of active cryptocurrencies, market share distribution and turnover of cryptocurrencies. 
2017 was an especially strong year for the cryptocurrency market, in part thanks to the ICO boom, with the aggregate market cap of all cryptocurrencies increasing in over 3,300%, growing from less than $18 billion in the early months of the year to $613 billion by the end of it. Bitcoin, the market's strongest coin, hit its peak price in December 2017 at USD$19,783 with a market cap of over USD$319 billion.
In spite of ICOs and ads promoting them being banned in a number of jurisdictions and platforms in 2017, the aggregate cryptocurrency market cap continued to climb until it hit a record high of $835 billion during the first week of January 2018 . However, this figure plummeted soon after. 
Early 2018 saw a downwards movement in the market, coinciding with increasing governmental scrutiny over ICOs and cryptocurrency trading around the world, in addition to the ban that Facebook, Twitter and Google applied on crypto related advertisements. Bitcoin's market cap dropped from around 290 billion in the first week of Januray to 111 billion on April 1st, 2018. 
According to Coinmarketcap.com, as of April 2nd 2018 the total capitalization of the cryptocurrency market was around 263 billion US dollars, spanning 1,596 different coins, Bitcoin dominating 45.5% of the total market with a market cap of USD$119.5 billion. Ethereum was coming in second with a market cap of USD$38,406,602,495, followed by Ripple's USD$19,569,896,039 market cap, Bitcoin Cash at USD$11,403,690,155 and Litecoin at USD$6,622,792,924. Up to date information on the cryptocurrency market can be found here.
Cambridge cryptocurrency market study
According to a 2017 study backed by the Cambridge Center for Alternative Finance and VISA, 31% of cryptocurrency companies operate across two cryptocurrency industry sectors or more, giving rise to an increasing number of universal cryptocurrency companies. Also, they have estimated that 1,876 people are working full time in the cryptocurrency industry, with this number thought to be well over 2,000 nowadays.
A survey conducted among employees in the industry shows most of them are universal in the cryptocurrency market. Most employees work for companies engaged in wallet infrastructure in the Asia-Pacific region (APR).
The study estimates that the number of users of cryptocurrency wallets ranges between 2.9 and 5.8 million people. The number of active wallets is estimated to be between 5.8 and 11.5 million. The boundary between wallets and exchanges is increasingly blurred: according to surveys, 52% of the wallets in existence provide currency exchange functions. However, unlike exchanges, wallets do not control access to users’ keys. Mobile wallets are the most popular wallet format. Desktop versions and online wallets come in second and third place.
The continent is home to 36% of participants in the industry, 27% of the exchanges, 19% of the wallets, 33% of the payement companies and 50% of the mining operations.
In second place is Europe, home to 29% of the total global industry, 37% of the exchanges, 42% of the wallets, 33% of the payment companies and 13% of the miners.
North America continent holds 27% stake of the total industry, 18% of the exchanges, 39% of the wallets, 19% of the payment companies and 33% of the mining.
With only 6% of the total participation in the industry, the continent holds 14% of the exchanges, a negligible share of the wallets, 11% of the payment companies and 4% of the miners.
Africa & Middle East
Lastly, with only 2% of participation from the grand total, Africa and the Middle East hold 4% of the exchanges, a marginal percentage of wallets, 4% of the payment companies and extremely few miners.
The forecasts for the development of the cryptocurrency market are diametrically opposed. According to some estimates, by the end of 2018 the volume of the current cryptocurrency market may exceed $1 trillion US dollars.
There are also analysts that are less positive, claiming the cryptocurrency market is a financial bubble that may burst at any time, letting the price of the bitcoin and other major cryptocurrencies collapse. This fear is mainly based on the fact that major cryptocurrencies are not backed up by any company, nor are there future plans or a product that might be scalable in time.
See Also on BitcoinWiki
- n.d., "Market", investopedia.com, n.d.. Retrieved 02.04.18.
- Abeer ElBahrawy et al., "Evolutionary dynamics of the cryptocurrency market", papers.ssrn.com, 17.05.17. Retrieved 02.04.18.
- Stan Schroeder, "The cryptocurrency market has been a bloodbath in March, but recovery may not be far off", Mashable.com, 31.03.18. Retrieved 02.04.18.
- Sean Williams, "The Cryptocurrency Crash Is Here, and This Is What's Most Interesting About It", The Motley Fool, 06.02.18. Retrieved 02.04.18.
- Ryan Browne, Arjun Kharpal, "Cryptocurrency market will hit $1 trillion valuation this year, CEO of top exchange says", cnbc.com, 13.02.18. Retrieved 02.04.18.
- author, "Cryptocurrency Market Capitalizations", Coinmarketcap.com, 02.04.18. Retrieved 02.04.18.