The data for the births are scraped automatically from the Health ministry's system and converted into an open format. Previous to 1. Jan 2012, many hospitals weren't connected, but since then the data should be precise. You could choose which date peroiod to show on the map by moving the sliders below. When clicking on a region on the map, you will see in the chart below the day-to-day statistics for it.

The population data is taken from the last census and are accurate as of Feb 2011. You can select an age group from the slider below. When moving over a region on the map, you will see how many births there would be monthly relative to 10000 people of the selected age group, if we take the data from the selected period of time.

Data on the birth rates from previous years is taken from the National Statistics Institute. As we don't have a breakdown by days or months, the calculations are made by taking the births for the whole selected year (for example: Plovdiv = 7248), dividing them by 365 or 366 and multiplying them by the number of days in the selected period (for example: 14). Then the data on the map represents the change of the current births relative to the average birth date in the past years. Thus for the first two weeks of 2012 Plovdiv is lagging behind with 4.68% relative to 2010.