The stock market just had its best first half of the year since 1998. Now what? History suggests investors will make more money in 2013’s second half. Since WWII, a big increase in the first half of a year has almost always been followed by more gains. Since 1946, the S&P 500 has risen 10 percent or more 23 times. In those 23 years, the market rose the second half of the year 19 times. The best second half was in 1954 — stocks rose 26.2 percent. The worst: 1987. The Black Monday crash was Oct. 19, and stocks fell 17.4 percent the second half. Of course, past performance is no guarantee of the future, and investors still face some hurdles.