  Decentralized exchanges are revolutionizing finance. With their ever-growing
increase in popularity, a natural question that begs to be asked is: how
efficient are these new markets?
  We find that nearly 30% of analyzed trades are executed at an unfavorable
rate. Additionally, we observe that, especially during the DeFi summer in 2020,
price inaccuracies across the market plagued DEXes. Uniswap and SushiSwap,
however, quickly adapt to their increased volumes. We see an increase in market
efficiency with time during the observation period. Nonetheless, the DEXes
still struggle to track the reference market when cryptocurrency prices are
highly volatile. During such periods of high volatility, we observe the market
becoming less efficient - manifested by an increased prevalence in cyclic
arbitrage opportunities.
