The percentage of games won by 14 points remains unchanged. So while the same key numbers are important, their order has changed. Note that 10 has passed both 6 and 4 in frequency. Effect on Lines For various reasons, even the distribution of the closing line itself has changed as the graph below illustrates. The occurrence of lines of 10 and 14 has not changed appreciably.
Different factors go into the closing line as opposed to the opening line.
The opening line is most likely determined by Las Vegas Sports Consultants headed by Roxy Roxborough and is only available to a few select wiseguys. Whereas the closing line reflects adjustments made to the line as money comes in on a game throughout the week and is not finalized until game time. It is usually in a sportsbook manager s best interest to have equal amounts of money bet on both teams so that they show a predictable profit no matter which one covers the spread. They do this by moving the line to attract more wagers to the team that is not being bet as heavily. So what this chart shows is not necessarily an increase in opening lines of 3, but an increased resistance to moving the line off of 3.