MUST READ: The Change in Womens Tennis | Thebigtip

The average age of the year end WTA top 10 was 26.79 in 2010, its highest level since 1979. Also, on the 31st January this year, the top 10 featured women from ten different countries, the first time this had happened since the WTA began producing computerised rankings in 1975. This two part article discusses the changing nature of women's tennis players and compares this to related changes on the men's side. This part looks at the increasing age of top players and the second part (coming soon) examines the nationalities of players.

The graph below shows the average age of the year end top 10 each year since 1975:

So after initially being very high (peaking at 28.24 in 1975; the first year of computerised WTA rankings), the average age of the year end top 10 reached its minimum in 1981 at just 21.73 years old. The statistic then generally varied between 22 and 25 before increasing to 26.79 last year.

While the average age of the top 10 is interesting, it may not be a good indicator of age trends across the whole tour as just one or two players can have a large influence on the average. The following graph shows the average age of the year-end top 100 every five years since and including 1990:

Unfortunately data for every year was unavailable, but the long-term age trend of the top 100 is very clear. At the very end of 1990, the average top 100 player was 22.80 years old, 20 years later and that number is 25.18; almost two and a half years older. This increase is due to their both being fewer young players and more older players in the top 100:

At the end of 1990, one quarter of the top 100 were teenagers compared to only six (approximately one in 17) at the end of last year. The youngest player in the top 100 of the 2010 year end rankings was Bojana Jovanovski who was 19 as of the 31st of December last year. This marked the first time since the WTA began producing computerised rankings in 1975 that no 18 year old or younger was in the year end the top 100*.

Conversely, there were only six players in their thirties in the December 1990 top 100 and 11 at the end of 2010, almost twice as many. Aging, but still highly ranked, all time greats such as Serena (29 years old) and Venus Williams (30 years old), are bound to increase the average, but  some other tour veterans are having their best ever years at around 30 years old. Francesca Schiavone won her first ever Grand Slam last year just a couple weeks shy of her 30th birthday while Li Na just reached her first Grand Slam final one month before she turns 29.