"Stockmarkets" vs. "stock markets"

It is Stock Market or equity market: (from Wikipedia)

• is the aggregation of buyers and sellers (a loose network of economic transactions, not a physical facility or discrete entity) of stocks (also called shares); these may include securities listed on a stock exchange as well as those only traded privately.

Definition of 'Stock market': (from Investopedia)

• The market in which shares of publicly held companies are issued and traded either through exchanges or over-the-counter markets. Also known as the equity market.

Ngram stock market vs stock-market

Personally I have very rarely seen it as one word. Ngram has no evidence of stock market as a single word.