Strategizing also plays a role. Numerous artists have taken deliberate steps to maximize their chart positions by such tactics as timing a single's debut to face the weakest possible competition, or massively discounting the price of singles to the point where each individual sale represented a financial loss. Meanwhile, other artists would deliberately withhold even their most marketable songs in order to boost album sales. Particularly in the 1990s, many of the most heavily played MTV and radio hits were unavailable for separate purchase. Because of such countervailing strategies, it cannot be said that a Hot 100 chart necessarily lists the country's 100 most popular or successful songs. Strategies like these were the main reason behind the December 1998 change in the charts.