GDP math problem

Can someone tell me how I calculate the annualized Australian GDP? If I take the last 4 numbers (0.5, 1.2, 0.2 and 0.7) and calculate what the total increase is then I get the number 2.63 % but on http://www.abs.gov.au/ausstats/abs%40.nsf/mf/5206.0 it is reported to be 2.7 %.

Her are my calculations.
100+100/100*0.5 = 100.5 %.
100.5+100.5/100*1.2 = 101.706 %
101.706+101.706/100*0.2 = 101.909 %
101.909+101.909/100*0,7 = 102.623

GDP increased by 102.623-100 = 2.63 %

What am I doing wrong???

Am I doing something wrong?

If the numbers that you give are correct:

1.005 x 1.012 x 1.002 x 1.007 = 1.02622777884 or 2.62 % (to 2.d.p) increase.

Maybe they used the actual figures (not rounded - it's very likely) to get the annualised GDP increase %. Here's an example to show how much higher it could be made by adding digits to the end of those quarterly percentages:

1.00549 x 1.01249 x 1.00249 1.00749 = 2.82% increase (to 2.d.p.)

A fair estimate of what the increase would be is gotten by adding '25' to the end of each of the quarterly % increases. This gives 2.72... % or 2.7 % (to 1 dp).

EDIT: I should say a 'fairer estimate' because for eg, the number which which was rounded to 0.007 could have been 0.0066 to 0.0074. Thus a 'fair' estimate would be the rounded number. It could have just happened that all the quarterly increases were closer to the upper bounds and thus had to be rounded down. This could be the reason for the difference: Annualised GDP increase % calculated using unrounded figures, and the quarterly figures you are using are rounded, thus you can't recreate the annualised GDP increase % yourself.

I hope this makes sense.

Thanks!

I added a little to the post, to be clearer.