1.   As futures fell, traders bought futures and sold the underlying baskets of stocks to profit on the spread, a practice called arbitrage.

2.   As futures rose, arbitrageurs sold futures to buy the underlying basket of stocks, thereby pulling up the benchmark index.

3.   As futures rose, traders then sold futures and bought the underlying basket of stocks, a practice known as arbitrage.

4.   As futures rose, arbitrageurs sold futures contracts and bought the underlying basket of stocks to profit on the spread between the two.

5.   As futures rose, traders sold futures to buy the underlying basket of stocks, thereby pulling up the benchmark index.

6.   That helped pull up the underlying benchmark Nikkei as arbitrageurs then sold the futures and bought the underlying basket of stocks.

7.   That in turn helped pull up the underlying benchmark Nikkei as arbitrageurs then sold the futures and bought the underlying basket of stocks.

8.   That helped pull up the underlying basket of stocks.

9.   That would likely pull down the underlying basket of stocks.

10.   The climb in futures helped pull up the benchmark index as traders sold futures and bought the underlying basket of stocks, a practice known as arbitrage.