Tokyo is the odds-on favorite to host the 2020 Olympic Games in the days before the winning city is announced, according to bookmakers.

According to OddsChecker.com, a website that gathers online gambling data, Tokyo, which last hosted the Olympics in 1964, has 44 percent of the bets placed. Madrid is second with a 29 percent chance of winning the Summer Games, followed by Istanbul with 24 percent. The speculation is giving a boost to Japanese construction and real estate companies.

Okasan Securities Group Inc.'s Tokyo Olympics-related stocks index has gained 45 percent this year, compared with the benchmark Topix index's 30 percent rise. The group of 79 stocks that may benefit from the games includes real estate, tourist companies and construction firms, including Yokogawa Bridge Holdings Corp., which jumped 62 percent this year.