Table 2.
Annual averages of PM2.5 concentration based on two types of years (calendar year versus seasonal year), two collections of monitoring sites (Guokong versus central region with 25 sites) and two kinds of statistical averages (simple averages versus (weather) adjusted averages). The asterisks (*) represent the level of significance for testing the increase/decrease of the annual change between two consecutive years (no asterisk means the increase/decrease was not significant; *0.025≤p<0.05; **0.01≤p<0.025; ***p<0.01).
| average |
annual percentage change (%) |
||||||||
|---|---|---|---|---|---|---|---|---|---|
| sites | form of average | year type | 2013 | 2014 | 2015 | 2016 | 2014–2013 | 2015–2014 | 2016–2015 |
| Guokong | simple | calendar | 81.3 | 87.1 | 80.9 | 72.6 | 7.1 | −7.1 | −10.3a |
| seasonal | 88.2 | 82.3 | 74.4 | 79.4 | −6.7 | −9.6 | 6.7 | ||
| adjusted | calendar | 80.6 | 84.9 | 76.8 | 73.4 | 5.3** | −9.5*** | −4.4* | |
| seasonal | 82.7 | 85.1 | 75.5 | 77.2 | 2.9 | −11.3*** | 2.3 | ||
| central | simple | calendar | 86.5 | 93.5 | 84.9 | 76.4 | 8.1 | −9.2 | −10.0 |
| seasonal | 94.2 | 89.1 | 78.0 | 83.1 | −5.4 | −12.5 | 6.5 | ||
| adjusted | calendar | 86.0 | 90.9 | 80.6 | 76.9 | 5.7*** | −11.3*** | −4.6* | |
| seasonal | 87.7 | 91.1 | 79.8 | 80.9 | 3.9* | −12.4*** | 1.4 | ||
aThe −10.3% differs from the −9.9% figure from the BMEMC as we have combined several data sources to lower the rates of missing values.